I just joined this forum so am a little late on commenting, but I have had internal vibrations for 3-4 months. Both my psychiatrist and my primary care physician say it is anxiety. I've seen a neurologist for tests of other types of pain and she didn't even comment on the internal vibrations, but then she doesn't comment on much of anything. I have them pretty much everywhere, but fortunately not all at once. They seem to move around.
I hope you are doing much better with your situation.