2002 Audi A4 Rattling noise at low speed (under 20 mph)

My 2002 Audi A4 1.8T Quattro is emitting a rattling sound from the engine compartment. There is no noise in the morning until I am exactly two miles from my residence. I notice the sound when I am under 20 mph and when I shift, say, from 1st gear to 2nd gear after I have lifted off the clutch pedal. Noise willl also occur if I downshift and go under 20 mph. There is no noise above 20 mph. The noise occurs whether I am on the accelerator or if I am just 'coasting'. It is clearly audible with the sunroof open or a window open. My car is regularly maintained at an Audi dealership; however, I have just recently relocated where the closest Audi dealer is 3 1/2 hours away. Is this an emergency? There is no change in temperature or handling. I would appreciate any tips/ideas. I am leery of using local repair shops...I am in a very small remote town.