It seems like you lack confidence.
When you find your self in this position again, try to change the scene. Don't be afraid to try things out. Experiment with your mind. Try teleporting yourself somewhere else. And make sure you're standing up with your eyes open. ;]
I've had this problem before, too. I would be standing up, though. But I was unable to move. No matter how much I tried. Even though I've only had 2 lucids, I come across this problem alot.