I agree, check your wheel bearings. Jack up each wheel, grab the wheel by the sides (never put your hand UNDER the tire) and give it a shake.
If you have jackstands, jack up both rear tires and give them a spin. Be sure to chock the front tires first!
06 330i 6mt Spt- Eibach Springs, BMW Perf Susp, Supersprint Exhaust, BSW Audio
94 325i 5mt 4d- M3 springs/susp, Z3 wheels, Chipped, Intake, Exhaust= FUN!