hello I am new to buying a Audi and I am looking into buying a 06 Audi A4 Quattro. The car looks amazing and feels like my next car. There is one problem, the car seems to vibrate when in (Drive) or (Rear). The car is quiet as can be when in neutral or Parking but when in Drive or in gear the car seems to shake a bit. The steering wheel does not shake but the seat seems to vibrate a bit almost like one of those massaging chairs. I have seen and test drove 2 06 quattro A4's so far and they both had that same shaking issue. I was just wondering if this is normal for A4's with quattro or is this something I should stay away from? By the way the car is auto not manual.

thanks for your help.