radio turned off by itself

While driving to work, the radio made a weird noise then turned off. I called Onstar to run a diagnostic on vehicle and it came back showing no problems with the radio. They then transferred me to Sirus XM to see if they could diagnose. They too were unable to help. Coincidentally, I traded my GMC Terrain for the Acadia because it was doing the same thing (along with lights turning off) and had taken it into the dealership and they were unable to duplicate the problem.