I've recently developed a sort of obsession with flexing my wrists backwards and hitting the bases of my palms together so my hands sort of vibrate. It hurts but I do it without thinking. I seem to do it more when I feel awkward or have a bad memory. I'm not sure if it's a problem really - I'm a little worried about accidentally bruising myself, but that hasn't happened so far - I'm more just wondering why I've started doing it.