I actually remember the day when something like this happened to me. I was nine or ten and playing on a playground merry-go-round. It was . . . intense. My mother called me into the house, and as I ran home I kept thinking, “I’m observing myself!” or words/thoughts to that effect.
I’ve been posting on the SDMB for over 14 years now, and have always meant to start a thread like this…but never got around to it. Plus, I was pretty sure people would think I was nuts or something. 
Anyway, I get a similar self-aware sensation every now and then. I clearly remember the first time it happened to me, walking along the sidewalk when I was 11 years old. I got this intense realization that what I was doing at that moment was REALLY HAPPENING RIGHT NOW. In other words, it wasn’t a memory of something that had happened in the past, or a scene in a book or movie, but was actual reality that was actually happening right now. To me.
It’s rather a difficult feeling to describe. I have since gotten this feeling many times since that first time, probably every year or two. If I think about it, I can sometimes make it happen on demand, rather like you can make yourself yawn by thinking about it.
Anyway, when this sensation occurs, it’s a little overwhelming. I sometimes get light-headed and dizzy. I also get very hyperaware about what’s going on at that moment. I can look around at my surroundings, and it’s like the first time I’ve ever seen them, even in my own home. It’s almost like I go through my normal life on autopilot, and when this sensation occurs, the autopilot is switched off for a few moments.
I also get a sense of my own mortality, that I’m 46 years old, and can clearly recall having the same sensation when I was in my 30s, and earlier in my 20s, and even earlier when I was 11…
August 29, 1997.
I don’t recall NOT feeling this way.
I recall being about 4 and thinking “I’m…me.” As in, I’m a human being involved in this thing called life. Which I think was pretty profound for a four-year-old.
I’m also glad you started this thread - it’s a topic I’ve been interested in for a while. It’s really interesting how most people tend to have the same philosophical “moments” at similar ages. It must have something to do with how brains develop and start to understand. In a way, I think we all experience these kinds of things, but they can be hard to communicate, especially at young ages, so we just start to believe we’re the only ones who have them. I’m not quite sure what kind of “self-awareness” you’re talking about, but I’ve got a couple:
When I was . . . around 6, or a bit younger? - I remember playing in a pool and talking to my older sister about how the only thing you can be sure of is your own consciousness. Of course, I didn’t think of it in those words - it was more like “Hey, I’m definitely me, becuase I know that, but I can’t know that you exist in the same way I do. What if you don’t?” Then my sister pointed out that there’s a whole philosophy based around the idea (solipsism), which kinda works against it.
I was 9, in 4th grade, when I remember standing in my bathroom and staring at my reflection at the mirror. I thought, “I will always remember this moment.” It was this overwhelming sense of knowing that this, right now, was my childhood - that one day I’d be an adult, that I’d grow older, that I wouldn’t really be me anymore. I would change. That I couldn’t hold on to this, this moment, this feeling of being exactly me. And I still remember that.
In middle/high school I had a similar feeling in a different form. I would be walking down the road when I’d start “talking” to my future self - the one two steps in front of me. I’d try to explain to that self how it felt to be me, wondering what being that 5-seconds-in-advance self would be like, saying goodbye to the slightly younger self every second. Yeah, I was weird.
In early high school, I’d get these really disconcerting dissociative episodes - I actually still get them. I’d be sitting in Chemistry or whatever, and suddenly I’d be aware of how . . . bizarre this was. Hands, fingers, eyes, spoken language. That little marks and dashes on flattened wood pulp communicate complex ideas. That we were so incredibly tiny, so insignificant, that I was wasting my fleeting years as a living, thinking being on trying to get straight As. It made it hard to memorize elements, I can tell you that. 
Tomorrow.
When I was maybe nine or ten, I used to internally narrate my activities, in the third person, as if I was telling a story about myself. I remember having a conversation about said narration with a friend, at the time, who said she did the same thing.
That’s the first thing that came to mind when I read the OP, but I don’t remember it being an “ah ha!” moment or anything.
Me, too. I have a vivid memory of where I was and what I was wearing when it happened.
I’m hoping it’ll be any day now.
I was around eight when someone said something they hoped would be funny but wasn’t. I remember clearly thinking that people are either funny, trying to be funny or not funny at all which then broke down into funny and not funny and that I was part of the funny group.
Jeez, I’m 52 and I still do that.
I also compose stories and poems about fictional characters pretty much nonstop unless I must pause to think about some real-world thing. But once I’m done with the real-world thing, I’ll pick up the story where I left it off.
This.
What I have seen many times is people becoming other-aware, in two phases: one, becoming aware that the world goes on without them (this usually gets you a child who doesn’t want to go to sleep - because damnit, if you’re asleep you don’t see what’s going on!), two, becoming aware that other people are… people. They’re not props in Number One’s life, they have feelings, ideas, they hurt, they laugh, they deserve respect (or not); some existed before Number One was born and some will be there after you’re gone; in some ways they are like you, in others, not at all. The people who never completely get the second bit are the ones layfolk call psychopaths.
I can remember feeling like I wasn’t my body, but I was somehow controlling my body from elsewhere. Like if I went to sleep I was just leaving my body there.
Kind of like a avatar in a game.
I also don’t recall not being self aware. In fact, sometimes I think I’m too aware…
Sometimes when I’m about to doze off to sleep, I’ll jolt myself right back awake because right at that moment, I become aware of myself, but I don’t feel like I’m inside my own body- I just feel like I’m merely existing.
And of course this all freaks me the hell out so the adrenaline kicks in and jolts me back awake.
I’ve often wondered if that’s what it feels like to die.
Hmmm I actually found this thread in response to another similar query of mine.
As in do you remember when you first realized that you existed.
For me it was when I was about 9 years old and all of a sudden…I Was.
I have absolutely no memories or feelings of anything before that time and I basically had to fake my way through life from then to now since I didn’t know any of these people. It pretty much forced me to mature faster yet I still can only consider myself mentally around 14-15.
In response to the actual intent of this thread, yeah pretty much All the time.
Children’s first inklings of self awareness, for example, recognizing their parents as being separate from themselves usually happens around one and a half to two years old, and I don’t remember anything nearly that far back. I do, however, remember being five or so, lying in bed, and suddenly realizing that my mother was going to die one day. As in, my mother was not a fixed construct that would be with me for my entire life. I thought about it in simpler terms than that, but that was the idea. Cried myself to sleep.
I don’t know if this is more in keeping with the OP’s question, but I remember being a kid, eight or so, and realizing that there were different levels of being myself and not being myself. In other words, my thoughts were who I was, and I could distance myself from me by thinking in the third person (“Small Hen is walking to school, she’s cold and wishes she has time to go back for her jacket”), and even better, I could think in another person’s thoughts and be them, in a way. It sounds like I mean playing pretend, but it was a bit more elaborate than that. I built entirely new personas (or borrowed them from favorite tv shows and people I knew) and lived them for days. As you can imagine, getting me to engage in school was an exercise in futility.
I still do this now at thirty, though I turn it on and shut it off more easily now, and I recognize it for exactly what it is - a coping mechanism for my anxiety issues. But as a kid, it did feel like a very philosophical concept.
I feel like I always realized I was ‘me’, right back to my first memory when I was about one and a half - I clearly remember my parents moving us to a new home when they were expecting my brother to be borne.
What I still have trouble dealing with is understanding that other people are the same way inside. On a logical level of course I know it exists, but on a feeling level it is just hard to accept.
Another step was realizing that older people were once young. I just thought were were all somewhat different looking I did not realize that I would one day age like my grandparents - that was unsettling.
I was walking to school thinking about how somewhere there could be an alien girl on an alien planet and wondering what she was thinking when I realised that I was a small person on a planet and I was thinking. It was like an eye opening in my head and I wish I could have that feeling again.
My earliest memory is being bathed by my mother in a baby bathtub. The headrest in it wasn’t very foolproof, as I recall my head sliding down towards the water and being unable to do anything about it. My mother would always catch my head but the experience was rather rattling to my infant brain.
Other memories include learning how to tie my shoes (my parents were going to take me for ice cream when I finally got it), and my mother had to teach me how to do it left handed; that was why it was so difficult for me at first. I also remember kindergarten, hating naps (I love them now), and feeling smug that I already knew buttons, tying laces, snaps, and so forth, that the rest of the kids were just now learning. In first grade I distinctly remember the teacher asking on the first day who already knew how to read, and instantly swooping those who could away to the advanced learning program. That was the only requirement and no testing was done. I was not one of them and I resented it all the way to 6th grade.