LaBerge mentions things about vibrations during WILDs. In his book Exploring the World of Lucid Dreaming, in the Attention on Body and Self section of the Falling Asleep Consciously section, he says:

If you focus on your body while falling asleep, you will sometimes notice a condition in which it seems to undergo extreme distortions, or begins to shake with mysterious vibrations, or becomes completely paralyzed.
In his Twin Body Technique and his One Body Technique in the same section he says:

Watch for signs of strange sensations, vibrations, and distortions of your body image.