It's after the car has stopped and is at a stand still. As I continue to let off the brake the car obviously inches forward but the noise starts as soon as i start to release my foot from the brake. Also, I don't notice it when it is really cold outside (less than 32 degrees).
I hate to say this, but I agree with your dealer. It's normal for the stock brakes to do this on the 300C. What's happening is that you are transitioning from static friction (higher Coefficient of friction) to sliding friction (lower Cf) and it's possible to apply just the right amount of pedal input as you lift off the brakes that you can make your calipers vibrate. It doesn't happen on all cars and it doesn't happen with all brake pads. It requires the perfect combination of conditions to make it start. Think about that crystal glass that you can cause to "sing" by wetting your finger and running it around the rim. If you press slightly too hard or slightly too soft or if you fill the glass, the singing won't happen. Again, it requires just the right conditions to happen.
All you have to do is lift off the brakes a little faster. Bedding in your brakes may also help by raising the sliding Cf and changing the input conditions that are required to make the calipers vibrate. Either way, you have the ability to slightly modify your driving style so that the sound does not occur.
Remember the patient who tells his doctor, "Doctor, it hurts whenever I do this!" And the doctor responds, "Well, stop doing that!"