Need to pop in here about the restless leg syndrome. I have this almost every night while going to sleep. I believe my RLS is caused by drinking coffee. Its scientifically known that coffee can cause RLS. So if your a coffee drinker it can be as simple as that.
To deal with it I kind of tense and relaxe my muscles in my legs, because I only have it in my legs. It goes away after some time but I aggree that it can be irritating in the middle of trance practice. Do as CFT writes, and then get on with your practice.

Cheers.