well it could be a couple of different things. your factory amp could be cutting out or your wiring harness behind the head unit might not be making a good connection. are u loosing the lights on the radio also when u loose sound? do u loose power or sound?
Either way its not a bad idea to upgrade your stock stereo. A cheap $150 Pioneer Head unit and cheapish 2 or 3way speakers will sound much better than the stock setup. I'm not sure what GM issue was, maybe their designers were hearing impaired. But there wasn't one GM stereo system that had good sound quality. Not even the Monsoon or Bose. But if u get into a ford with a Mach Audio System u would be impressed, (my dads Expedition had a Subwoofer built into the rear and it actually knocked, and u could hear it from the outside).
1992 Bonnie SE, freshly overhauled, 6000k HID'*, SensaTrac Struts, 32mm Tubular SSEI sway bar
Kenwood HU , JL 1000/1, 8W7'*, 15" CVX'*, 18" DC lvl4