Maybe it's a Kriya, but it may be perhaps because when your eyes are closed you don't have a physical reference for the horizon and your sense of balance becomes subjected to energy movement. Try opening your eyes momentarily if it becomes a problem, and also try tightening your gluteus muscles and see if it helps. It's actually a device used in yoga, although I can't remember its 'official' name.

On edit, it's Muban.