A Regular Night Shift Habit

I've been working as a bartender at this dive bar for years now. Every night around 2 AM, after the regulars have thinned out and before the early morning shift starts, I find myself compulsively cleaning glasses even when there's nothing to clean. It's like my hands have a mind of their own, polishing away until my arms get sore. Does anyone else feel this need to keep busy late at night? Is it just me or is this normal?