I had a 96 Blazer with similar problem. Turned out to be in the radio circuit. Pull the fuse that serviced the radio and it was ok.
Sorry, this was a beater, parts car, that was bone yard bound and I never did actually repair the problem. Darned thing also had a glitch in the wiper circuit. If it was cold and dry outside, the wipers would work. If the temp got over 55 degrees, or rainy, no wipers.
The cruise controll would activate the throttle at any time, for no reason, with switch off and sometimes at almost a stop. Strange gremlins in that thing..