I have that sometimes. Got it last friday infact! Very annoying. But i found that if i stopped thinking about it it eventually went away. One time it was so bad i was actually sick (one of the worst experiences of my life).
I also get the feeling that all my muscles are really tight (on a pretty high dose anyway) and that any movement i make i will pull all the tiny muscles (fingers etc).
No drug, not even alcohol, causes the fundamental ills of society. If we're looking for the source of our troubles, we shouldn't test people for drugs, we should test them for stupidity, ignorance, greed and love of power. ~P.J. O'Rourke