I'm not sure about quirks. I have a few things that are habitual, but if it doesn't happen, I don't sweat it.
I typically fall asleep on my left side, but that's because my wife sleeps to my right and I get hot and roll that way. If we stay in a hotel and go to opposite sides of the bed than at home, I sleep however suits me. I have slept fully clothed, in underwear and naked. Doesn't really matter, but I usually sleep in underwear because our dogs sleep with us and I don't want them discovering a play toy. No sir!
My OCD was gone by the time I was a teen, so all those typical OCD things don't exist. I can pop one finger and not pop the other, I can leave water on the counter or eat a sandwich with filthy hands.
I guess I have one unexplainable quirk that I can think of. I'm afraid of heights, but I have to be pretty high up first. The wind makes it much, much worse. If I looked over the edge of a 3rd floor roof, I would probably be in controlled fight-or-flight mode.
I have a hard time in pools, but that's because I nearly drowned in one as a teen. I've worked through most of that fear.