Is tapping someone's shoulder with your finger for a bit too much skinship? I feel like that isn't, especially if it's a fraction of a second and aimed not at the back side of the shoulder. Maybe I'm the weird one.
I had pretty bad insomnia and my classes were in the morning period in middle school, so that is THE most relatable, though after a few months most teachers wouldn't mind anymore and would just let me sleep, i was very grateful!