I used to sleep with my arm (wrist, really) tucked between my knees, but I started to have a long-term tingling sensation in my fingers. I was pretty alarmed about this development, but my doctor randomly asked me how I slept and when I changed my habit, the tingling went away. I’m glad he asked me because I never would have connected those two things.
This.
(tucked between kenobi’s knees)
mmm
I was torn between “forearm facing my face” and other. Usually my arms are both curled around a blanket, and more or less folded against my chest.
??? The poll is for people who sleep on their sides. It’s in the thread title. If you’re not one, why complain about the OP’s assumptions?
To answer the OP, I have an unusual situation (I chose ‘other’) in that the head of my mattress is just a bit pushed away from the wall (no headboard), plus I have a mattress topper. Since I sleep on my right side, this setup lets me slip my right elbow down into the small comfy niche between the memory foam topper/mattress layers and the wall. It’s really helpful for both supporting the arm and putting no strain on my muscle, not to mention letting my spine be relatively straightish.
I think I’ve seen wedge-shaped pillows that pretty much mimic my setup (letting you slip your arm into a pre-cut hole in the wedge) without needing the mattress niche.
I do sleep on my sideS, but I keep changing position; while it is always on my side, my position and therefore the position of my arm are not fixed. In fact, which side (and, therefore, which arm) are not fixed. “I sleep on my side” and “I do not sleep in a fixed position” are not contradictory. You apparently managed to miss the whole rest of that line.
I went head but usually its more under my neck or with my hand under my face and the arm folded out at an angle.
“Those aren’t pillows!”
I voted forearm, because that’s maaaaybe most common? But the real answer is:
Also, while I usually sleep on my side, I also sometimes sleep on my belly or even my back.
My arms are folded across my chest, with my lower hand tucked into my upper armpit. I’ve noted when I’ve seen pictures or reflections in a mirror that it looks terribly uncomfortable, with my wrist bent at what seems like an awkward angle. I actually find it quite cozy, though, on eirher side.
Mostly with my arm straight out under my ‘arm’ pillow, and the other arm straight out on top of my arm pillow. I sleep with 5 pillows: head pillow, arm pillow on each side, leg pillow on each side. When I turn over, I already have the necessary pillows for my arms and legs to rest on/under.
If I don’t use the arm pillow, I lay on my arm too much and too hard, resulting in a numb arm and eventual pins and needles. That will ruin an already iffy night of sleep.
Sometimes I find myself with my arm bent and hand under my pillow or cupping my face. This usually makes my my arm go numb, pins and needles, waking up. I try not to start my night that way.
He’s not nearly as mean as his user name would lead you to believe. 
Tucked under my pillow. (Which in turn is under my head, but it’s not the same thing.)
This is me too! I always start out on my right side with my right arm kind of wrapped in front of me sometimes holding my left shoulder. If/when I switch to my left side I move my pillow kind of long-ways with my left arm under it and my right arm hugging it. I cannot switch those positions. Like you said, very uncomfortable.
I assume I move around through the night but my “settling in” position has my arm tucked between the two stacked pillows under my head. So I chose Option #1.
I sleep with my blanket over my head. I wrap it around my eyes and poke my nose and mouth out to breathe, then hold the blanket shut at my chin. Which means that my arms are curled up at my chin. I think. I never actually gave that much conscious thought to the exact position that I sleep in, so if I go to sleep tonight and discover I was wrong, I will probably feel compelled to update this thread again tomorrow.
I am clutching a big teddy bear. I had always used a pillow but my kid got this huge bear about 10 years ago and I found it was the perfect size for my arm, plus it was firm and never went flat. I’ve been cuddling that Harmony Care Bear since that day. Now I have trouble sleeping without it.
For me it varies. Sometimes tucked directly under my head, sometimes under the pillow, sometimes at my side - either straight out, or elbow bent. I do whatever feels most comfortable on any given night.
What are these “head” and “leg” things of which you speak?
I’ve recently started sleeping with my arms crossed across my chest, while on my left side at least, which is the most comfortable side and the side I spend the most time sleeping on.
I find that I pull my pillow up between my shoulder and my head so that my neck is straight, my shoulder is on the mattress, my upper arm points down around 7 on a clock, my elbow bends and my forearm points somewhere around 11 on the clock. I move around a lot, and sometimes sleep on my stomach, but when I move to my side, that is where the arm goes.