I didn't realize it when I was younger but singing is my biggest stim. Unless I am majorly depressed to the point that I am only breathing and blinking, I am singing just about all the time. (It's actually a good way for me to measure how depressed I am.) I even sing and hum in my sleep. If I'm somewhere where I have to be quiet, I'm tapping my foot or hands to a beat or I'm writing lyrics.
And more than that, every waking moment, there is a song stuck in my head. And I don't mean just the lyrics. I mean every word, instrument and sound in the song is playing in my brain as though I'm listening to it.
Does anyone else sing, hum, or do something musical to stim?