Metal Rattling Noise at Start-up

Has anyone experienced or heard a brief but LOUD metal rattling noise at engine start (like two small metal plates rattling against each other)? The service department at my Infiniti dealer stated that he has located a service investigation ticket within Infiniti about "intermittent" metal rattling noise at startup. Trouble is, it is not intermittent in my car - it happens EVERY time but is much louder with a cold start. It drives me bananas that a $45K car makes this rattling noise. It is a brief noise that stops quickly, and does not continue as the engine runs. I have been assured that this is not a mechanical problem and does not affect the integrity and safety when operating of the car. But I have had people ask me if my brand new car is okay when they hear it start? It's embarrassing! Anyone have the same experience?

We have only had the car for 3 weeks and drove it a couple times, but my son (who has decided its his new car) has mentioned he hears something that sounds like a heat shield rattling at start up. Once it warms up and dries up a little, I can pull out the creeper and look around, but only if the car is around ;-)

I thought it was just me too that had the rattling noise. It does sound like the heat shield.