So I don't have any absolutely specific concerns, just a one thing I think may be a bit odd. First I should mention, I'm 22 years old

I've had these instances since I was little where all of a sudden my whole body would just shake for a second or two. It would be completely uncontrollable, depending on how intense it'll be. I'll feel this tingle from the back of my head at the spine, and then all the way down the spine. It doesn't last long, and it happens more when I'm cold or tired. They're not like the common chills, I know those you would get from being cold, just a sudden full body shake. It doesn't even typically accompany goosebumps, so it's something other than those common chills. Sometimes I won't get the shake, but I'll feel that kind of tingle going down my spine. Only other way I can describe it is like cold, silvery, shiny metal (don't know why I associate it with that, it just seems like metal to me).

Not sure if it's anything to really be concerned about, it's really just some weird thing that happens often. My only guess is a mild random electrical misfire in the brain, like those with epilepsy (if I'm understanding epilepsy correctly). Just thought it would be nice to know if it's anything at all, because it just doesn't seem like a normal thing to have happen.

Thoughts?