If you awaken from a dream and don’t move at all, it is very easy to re-enter the dream. It’s a good way to prolong lucid dreams, and can also be used from normal dreams to become lucid (though that takes some discipline). Dreaming is sort of like a meditative state, and as long as you don’t move your body, it’s very easy to continue. Anyway, that’s what it sounded like to me… If you want to read more, click here…
Also, what do your vibrations feel like? If they feel electrical, like sticking a fork-in-an-outlet, you might want to just try moving your body while the vibrations are occurring, rather than waiting for hypnagogic imagery. For me, the vibrations are a signal that I am already dreaming, and attempting to move will cause my dreambody to move instead of my realbody…