Does anybody know why I keep having muscle spasms?

As far back as I can remember, I've been having random muscle spasms. Now, they're not big, awful things, just little twitches once about every 10-30 minutes. Usually, they don't do any damage, but they sometimes cause me to drop something, which can potentially lead to injury. They always happen in a part of my body that I'm not moving a lot, so it can be my legs, arms, hands, fingers, or any other part of my body, really. I have a serious anxiety problem, too, so I thought this may just be a result of all the fidgeting I do, but I would really love to have a straightforward answer that helps me get to a conclusion.