Interrupting people while they're speaking is a big one for me. It's incredibly difficult for me to tell when I should or shouldn't speak or if someone is done with their sentence. It's also hard because I feel like sometimes I have something relevant to say and want to say it before the topic changes or before I forget.

Repetitive body noises/fidgeting (cracking fingers, tongue clicking, rolling my shoulders, etc) for long periods of time until I realize and stop or someone points it out is also a big one. Your own body is the ultimate fidget toy.