Ahhhh, I think I know what you mean but I've just not called it 'vibrations'...
So, as I increased my estrogen (to levels which turned out to be too high), I would be lying in bed at night feeling myself literally throbbing and pulsing against the mattress. It actually felt like the mattress was moving at first - I thought it was my husband scratching himself next to me, but it went on and on and on and when I sat up, he was asleep
Then I realised it was coming from me. Which was a shock.
As I've reduced my estrogen back down again gradually, the throbbing has reduced too. When it is minimal, I would say it feels like I am just a little shaky or fluttery or trembly - and is easier to ignore.
So for me, this comes from the estrogen somehow not being optimal or my body not having adjusted to it. I actually think it is an episode of higher than usual blood pressure and that's what I'm feeling pulsing - the blood through my veins.
I don't know if that helps at all or if what I'm experiencing is your 'vibrations', but that's what it calls to mind for me...