Over the past few months I've begun to have weird muscle spasms/jerks. To start with the spasms, it feels like either one of my legs or both + my torso involuntarily tense up and start shaking, kind of like a cramp but somewhat different. It's like when you tense all the muscles in your arm to make your arm vibrate. It usually lasts from 5-20 seconds. For the muscle jerks, it feels like I suddenly, subconciously, jerked either my leg or my neck to a position, without even thinking about it. Also, I have the spasms in my upper arms and neck where they will all tense up and lock into a position, not vibrate, but it has a similar tensing to the spasms listed earlier.