Just wanted to say I get this too, just on my left leg. I'll feel it for a fleeting moment then test incessantly while walking / standing around, by hopping from leg to leg like a flamingo. I never feel anything when I'm expecting to feel it, but then it will suddenly pop back up again. For me, I definitely notice that it's something to do with how tense my lower back / butt is. Probably repeated testing (as I have been doing) will only stress out the muscles in the are more.