I click my teeth all the time and, like someone else mentioned, it's a while before I notice I've been doing it for half the morning or "all day." I believe it started up after I moved into a temporary apt. last year. It's very common and starts up before I even know it. I don't grind, though, but I'm hoping to hear from other teeth clickers: repetitive joining of the upper teeth to the lower while mouth is closed, up and down, up and down, up and down, while on computer, watching TV, shopping, driving, etc. I have no idea why it starts up.