This doesn't happen often (maybe once every 3-4 weeks) but it is strange when it does. Sometimes I get really excited when listening to music, y'know.. regular euphoric type stuff just sitting back and relaxing. Sometimes, very rarely, my hand might "lock-up" and I won't be able to move it for 10 seconds. Kind of scary, but like I said.. doesn't happen very often. I'm fairly young.. only 24. Decent health, thin, workout every week. I'm also on no prescription drugs. Anyone know what this is or if it is (or can be) serious?