A Stimmy
Stimming is when you do weird things with your body, like flapping your hands or bouncing around like a crazy person. It's what autists do when they're happy, sad, or just plain confused.
I was stimming in class because I was so excited about lunch.
Stimming at the mall because my brain is overloading.
Stimming while eating cereal at 3 a. m. Classic me.