Don't forget that you are SUPPOSE to fall asleep. That is the whole idea with WILDing. You may be focusing too much, or trying too hard. You want to allow your body to fall asleep, but you want to be consciously aware of it. Once you get these vibrations you speak of, relax your entire body, every single muscle. Then watch the darkness, feel the vibrations, and listen to the sounds as you allow yourself to fall asleep. Don't focus too much attention, just focus enough that you stay aware of what you are trying to do. Good Luck!