Does your camera "lift"?

In article , Dingo
wrote:

Imagine you are at a red light. When the light turns green, you stomp
on the gas. For a very brief second, the car's front end feels as
though it lifts up.

Similarly, I have a Nikon D100 mounted on a Manfrotto 3039 head, aimed
outside at a bird feeder. FWIW, it's a 24-120mm lens, currently set
around 80mm or so. When I press the shutter release halfway to
focus, I see the image shift ever so slightly in the view finder, as
if the lens has lifted minutely.

assuming that your 24-120mm is the version with vibration reduction,
then what you are seeing is the lens attempting to stabilize the image.
turn off the vr system and you shouldn't be seeing any 'lift.'