Examine very closely the connectors that plug into the back of the radio for any loose or weak wires. The wire is weakest where it goes into the crimp and that's where the problem usually is. I just repaired the shift interlock on my '98 because two of the wires had come apart at the crimp. These wires are buried inside the console and were taped/restrained well but it happened anyway.
Edit: "UQ3" is "Speaker System, Performance Enhanced Audio". You do have an amplifier.