This has been happening to me, but only since the weather got cold. It may be nothing to worry about, but it is very disconcerting because it is loud, and the car shudders. I have tried stepping on the brakes a few times before I start moving, and this seems to help, sometimes, but not all of the time. I would love to find a way for this to stop happening because it really bothers me, even if I know it is nothing to worry about.