OCDBenz

Remember when we were kids and we would use a clothespin to attach a playing card on the spokes of a bicycle to get a "engine" noise? Okay, maybe I'm revealing my age, but that's the sound my 2012 C300 4Matic Sport makes, mainly before it warms up. It starts at exactly 28 MPH and continues to about 40 MPH. I happens for the first 10-12 minutes of driving, then it's gone. It's not real loud, but definitely noticeable and very irritating. It almost sounds a bit like a fan coming on at 28 MPH, but I'm sure it is not. Could it be the transmission? I'll probably bring the car in to the dealer soon, but wanted check to see if anyone else has experienced this, or maybe has an idea of what it could be. Thanks.