For decades, I’ve worn my hair microshort (beyond Pixie cut-short) … have started growing it out for the past 9 months or so. It’s grown longer, and now is wavy – in spots. I never knew I had hair that would do that.
I think I “know” about twisted hair follicles making hair curly.
There is ONE particular lock that I am almost constantly turning, twisting, tugging, etc. You get the idea.
Why?
I think we all do that. Well, if our hair is long enough. I play with my forelock when I’m trying to fall asleep.
That sounds dirty! Forelock=the middle of my bangs.
I remember trying to stop the hair curling/twisting in my teen years, and my aunt found out and laughed at me. “You’ll never stop that,” she said; “You’ve been doing that since you were in your crib!”
I gave up trying.
Because it’s there? Because you can?
I’ve always seen women playing with their hair as flirtatious, but it sounds like you’re doing it when alone too. Are you growing your hair due to a new relationship you’re in, or hoping for?
It’s known as trichotillomania.
I don’t think that this is the case for the OP since your link states in the first sentence
I don’t see anything about it disrupting their life.
I would say that it’s genetic. I know that my grandfather did it, my father does it, I do it and one of my children do it as well. I also know that on my father’s side of the family one or two uncles and aunts do it, a few of my cousins do it and some of their children do it. It also seems to correlate strongly with the biting of fingernails.
IMO, twirling the hair is simply a self-soothing motion. Totally harmless. It does not fit into the Trichotillomania classification unless the hair is being pulled out. I’m sure that people suffering from Trichotillomania would love to be able to stop with just the twirling action.
I agree with Edward about it running in families. I have two family members with “trich” (eyebrows and eyelashes) and a brother who twirls his hair and bites his nails. I’ve used to pick at my split ends as a teenager. I believe that there is a over-grooming gene that has yet to be discovered!
Desmond Morris, the author of The Naked Ape, says that it’s an evolutionary thing. Or more colloquially, it’s chicks flirting, saying “Look, I’m making myself prettier for you!”
I notice sometimes that while idle at the computer, I end up picking something up off the desk to “fiddle” with without making a deliberate decision to do so. It might be a pen/pencil, a post-it note, whatever. If nothing is around, I’ll end up toying with my moustache. (I got the short bristly kind, not the kind you can twirl the ends of. 
) Almost as if my hands need something to do.
May I assume that this is related to the the same absentmindedness fidgeting that the OP is discussing?
(I do not accept the explanation that I’m trying to give my computer any “I’m making myself coy and cute for you” signals.)
I once found myself sitting behind a compulsive hair twirler in an economics class. As a male with long hair I had never tried twilring my hair. I copied her method scrupulously and found it rather difficult to break the habit.
Did this myself when I was a long-haired freak. Just one of my several “nervous habits,” though they’re not necessarily associated with nerves. I’m also a leg-bouncer, a pen-chewer, and–apparently rarest and certainly most irritating to me–a shirt-collar-chewer. The leg thing is more or less all the time, not connected to anything in particular, though I may do it somewhat more when I’m anxious. Pens and shirts are sometimes an absent-minded thing, and often a thinking thing.
They’re all things I can control–I’ve gotten significantly better about shirts since ordering a bunch of eccentric Ts from shirtless that I don’t want ruined–but it’s an effort.