I hear a clicking sound when I go in reverse "click" and back to drive "click" . At a stop light, letting go of the brakes to press the gas then I hear it again. Click, click then it's gone. I thought it was the brakes but it's not. Getting worse.

What's going on?

 

Their was a TSB issued for an axle clicking noise. https://www.myg37.com/forums/tsb-tec...ear-axles.html
I had this problem and it was easily fixed by the dealer. It involves applying more grease and retorquing the bolts.