My spasms are very interesting. You can actually see the muscles jump up and down. The fun one is my abdomen. It looks like a scene taken from the movie "Alien".

It feels weird, like I stopped moving but someone forgot to tell my muscle that. It's also a little like the feeling one has touching the skin of a kettle drum while someone is keeping a fast beat while they are striking it. (hope that makes some sense).
They are different than jerks or tremors, which I also get from time to time. I tried Baclofen, couldn't handle it very well. Then my neuro had me try magnesium, helped a little. I mainly get the spasms when it's humid out or a major storm front is coming through.