Sounds pretty much like the motor mounts, though sometimes some people say it gets better with AC on because the idle up with it on.

A test someone posted (twinturboGTR IIRC) was to put it in drive, step on the brakes, engage park brake, (chocks would be a good idea too I think) then goose the throttle a bit.

IIRChe said broken mounts will cause significant engine movement doing this

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04 X5 3.0i auto
03 X5 4.6is