Wheels will bounce if they're very far out of balance. The bounce is usually not speed dependent though.
For wheel bounce that's in a narrow speed range, such as very bad between 60 and 70 but smooths out at 80 is due to harmonics in the suspension components.
The first place to look is the lower thrust arm bushings (also called tension struts).
#6 in this diagram:
https://www.realoem.com/bmw/enUS/sho...diagId=31_0521