I know exactly what you mean. I get that feeling almost every time I WILD. Those vibrations are very common. It is one of the last things you feel before transitioning to the dream. You were entering REM sleep. Keep doing whatever it is you were doing to cause this. You were very close. I will normally feel two or three waves of these vibrations before I can enter the dream.

Next time you get this feeling, imagine yourself doing something tactile, involving movement and touch. Just pick the first thing that comes to mind. You can even use a recent and familiar memory. It is time to leave your real body and become this new, imagined, dream body.