When I get really nervous, I play with the scar on my head.
Smooth, heavy hair running through my fingers feels sensual and soothing.
I've played with my hair since childhood. Twirling a strand of hair is an absent-minded habit.
p.s. It's called a nervous "tic," not a "tick." (https://www.google.com/search?q=ticks+images&oq=ticks+%2C+images&aqs=chrome.1.69i57j0l5.7642j1j9&sourceid=chrome&ie=UTF-8
Mine is being chatty. I get really chatty when all I really want to do is suck that cock or ravish someone. Especially a cutie like you.
Pretty rare I get nervous, but I get motionless and quiet when I do.
Conditioning.
I fidget with my hands. Wring them....don't know what to do with them, try to find something to hold and fiddle with.
I also tend to push up my glasses a lot.