I would check with your doctors. they can tell you if its because of medications or any health related issues.

people do have different things they do when they are not thinking about it. these things are called mannerisms/habits. Some people without thinking about it twirl their hair, others suck their thumbs or fingers, some people tap their fingers together, some people bounce a leg or two. some people snap their fingers, crack their knuckles, lick their lips, tap their fingers on table tops, some people trade on established habit/mannerism for another. I twirl my hair, cross and uncross my fingers, crack my knuckles. my doctor says for me it has nothing to do with any mental disorders, physical disorders, and nothing to do with my meds, just the way I am and its natural.