HELP With Strange Noise RE: 2010 C6 With 12,200 Miles

Following EVERY cold start for the past 3 months, I idle the car for 1 minute (as I always have)  before  slowly backing out of the garage, down the driveway  then onto the street.  I exit the driveway slowly with the steering wheel turned sharply right to protect the air dam from striking the culvert between the drive and street. Once the front wheels have entered the street, I straighten the steering wheel, come to a full stop,  engage first gear  then move off slowly.  Within 1-3 seconds of moving forward, I hear a single metallic "clunking" noise from somewhere below.  I neither feel anything in the steering wheel nor see any messages on the DIC.
I frequently reproduce this noise if the car sits outside in a parking lot for at least 30 minutes. Note: This is not the Evap Cannister clicking noise. The local dealer has no clue.