Friend, I have the same problem. It started as a vibration when stopped on a red light while pressing the brake pedal. It only happened on D and R, if you put in N it was just smooth.

I tried everything. Replacing motor mounts was the first, then camshaft sensor, plugs, filters... you name it. Today on the road it just got worse. It started shaking when accelerating from 80KM to 100KM and the vibration is now shaking the mirrors at idle.

I've researched a lot about this "vibration" and couldn't find anything conclusive. It seams to be a BMW gremlin, as you can find it related to different BMW models.

Now I'll check the front transmission (!!!???)
If this work out I'll gladly post it!