If I'm trying to get to sleep, I sometimes think of a part of a word e.g. - ate, and then go through every letter, well, consonant in the alphabet to see if it will make a proper word. So, bate - 👍cate - 👎 date - 👍etc. Actually, that's probably not weird, just dull and methodical, which is what's needed.
I also like to tear my toenails off (to trim them, not ripping the whole nail off, obviously) rather than using scissors.
I have to eat meals in a certain order. Vegetables first, then the protein part, lastly the carbs. Always in that order.
If I'm listening to my own music, not just the radio, I can't stop a song mid way through. The house would have to be on fire, someone in danger, or my DH come to tell me that someone we knew had died, something really serious. Anything else can wait. Sometimes I'll be needing the loo, and have to cross my legs till the songs finished. I also also listen to albums in their entirety, but I will pause between songs if need be.
I always pick my scabs off that I have, I just can't leave them be. 😳
Volume level on anything can only end in 0, 5 or an even number.