Electrical problem
1996 GMC Suburban V8 Four Wheel Drive Automatic 125000 miles

While listening to the radio at normal levels, for no apparent reasons, the radio volume raises to a deafening level. i am able to turn the volume down when this happens. I turned the speed control volume control off. I have replaced the radio with another stock radio and I still have the same problem. Any assistance would be appreciated. This problem almost caused my wife to crash, because the high volume startled her.