I’m not diagnosed, but I stim a lot. When I’m happy I shake my wrists or flail my arms a little and sometimes I bounce up and down. When I’m stressed I rub my hands together in a regular motion and/or scratch myself (arms and neck) and swing from side to side. I also rock a lot, both when happy and stressed. When I eat something I like I kind of wobble the spoon or fork in my hand and as a child I used to hum while eating, but I’ve since stopped doing that. Something I always do no matter my mood is tapping my fingers to the music that’s currently stuck in my head (I always have a song playing in my head or sometimes sentences or funny sounding words, idk why). I used to try and suppress those stims, but I’m much happier now that I mostly embrace them (at least when I’m alone or with people I trust).
Definitely read The Anatomy of Story if you’re a writer/interested in writing as a craft. It is by far the best guide on plot structure I have ever read and even though it focuses mainly on Hollywood plots it can be adapted to any story form. I use it as a starting point for everything I write, highly recommend it!