I just noticed that I whistle constantly. This started earlier this summer when I met an expert whistler and realized that I had lost my ability to whistle. So I kept practicing and now I whistle ALL THE TIME. It annoys the crap out of so many people, but I don't even know that I'm doing it!
I also do this other weird thing. You know how you cluck your tongue? Well, I do it with my bottom lip. It's weird. No one ever knows what I'm doing, but, yeah...
At the end of the school year I used to randomly start doing tongue stretches. That's when you really know you're an actor, huh, when you get the urge to do your voice warm up and don't even know you're doing it!
So, it's not just me, right? You all have these annoying habits too?