i just bought an 07 328 i sedan about a month ago, and i absolutely love the car, and have had no problems with it until the other day i started hearing a noise that sounds like its coming from under the car. when i hit the brake, the noise sounds like a rock or something slides from the back of the car to the front, and when i accelerate, it does the same from the front to the back! i've removed everything out of the car, and made sure it wasn't something inside the car rolling around, but the noise continues. it litterally sounds like there is a rock under the car, and everytime i brake or accelerate it rolls from one end to the other! any ideas??? thanks so much for the help!
oh yea...my driveway is partially gravel, about a quarter of a mile. so this could contribute to the "rock" possibility

Bring it in for service. I bought a 2006 550 last year and had to bring it in SEVEN times for issues in the first six months. (Will I buy another BMW? No.)

You may have to bring it several times before they find the problem, but the service departments try very hard to resolve the problem

You might also post this in the beemer forums for more specific help.