i have alot of similar things that i do...like adding things up/counting or drinking gulps or chewing a certain ammt of times on each side of my mouth or tapping something 2 times with my left foot so i have to tap it 2 times with my right foot so they equal each other...stuff like that. i think it's a combination of ocd symptoms and anxiety (at least for me) like if i make up rules and do things in a certain order/way it makes me feel better/lessen anxiety. usually i do it and dont fully realize that i'm doing it until after i've been doing it for 10 minutes or something. sometimes i'm aware of what i'm doing but do it anyway because it makes me feel in control and helps my anxiety lessen. i'd say it's pretty common. alot of people tap their pencil or tap their fingers in time when theyre anxious. i'd say unless you feel like it is hindering your daily life somehow, you dont need to see a dr. if it gets worse/more frequent/bothers you more, i would bring it up to your GP. ♥