I experience similar things. I have a tendency to hum something, usually very tuneless when I am nervous. I didn’t even know I did it until someone pointed it out to me (in a very abrupt and unkind way).

I also can’t stop tapping my feet up and down when I’m sitting down - it’s definitely a nervous/soothing thing, but it really used to irritate my work colleagues whenever I sat near them or was in a meeting with them.

I’ve managed to break the humming habit, but the leg bouncing still happens. I have been a highly nervous, anxious and stressed individual all my life, and I think these habits are a manifestation of that.