Shaking/Spasms when excited/nervous & randomly
 

So, I've been noticing that at random times I'll seem to just put both my hands either up against my chest or straight down, lock up all the muscles in my arms, chest, and stomach, hold my breath, and then just kind of shake really really fast for like maybe a couple seconds or so. I tend to do it a LOT more often when I am either excited, or nervous. I'm not really sure why I do it, it just kinda happens. I'll get urges to do it too, it will annoy me until I finally do it. I can even be triggered by things, like thinking about it. This thread is taking really long to write cause I keep on doing it. I usually only do it alone, but it can get so annoying sometimes, that I'll do it in public. Although no-one has ever said anything.
Also, when I was younger, maybe like 8-12 or something. I would do that exact same thing, except I would put the 2nd joint on my index fingers, from both hands, on the side of my nose. I will rarely do that anymore, but it happens sometimes when I get out of control.

I was wondering if anybody else had this? If anybody knows what this is? Should I be concerned, especially because I try not to do it?

I think everyone has little tic-like movements that they do without thinking and that in itself is nothing to be particularly concerned about, however it sounds like it is getting in the way of your everyday functioning, so perhaps seeing your GP (do you call them that in the US?) would be a good idea?

Everytime I do it, I know that I'm doing it, even though I don't want to sometimes.
Not really sure what GP stands for. But, even if I did see someone. What would they when be able to do?