D800 sensor cleaning - perceptible vibration?

Hi all, I have had my D800 for four months and I am not sure if the menu activated sensor cleaning function has ever worked. Should I be able to feel a small, but nevertheless perceptible vibration from the camera during cleaning?

I am confused because on ONE occasion when the function was activated, I DID feel a vibration, but only on that one occasion, though I use the function often. I do not use VR lenses. I have a gradual buildup of spotting on the sensor (I appreciate that the function cannot deal with sticky or moist particles). I'm sure every D800 owner has used this function, so feedback to know one way or the other would be much appreciated.

Many thanks.