On vehicles with intermittent windshield wipers, the wiper motor circuit board may fail and cause the wipers to stop working at times. Replacing the circuit board should resolve the issue. Some vehicles were recalled for this problem and some were not. You will need to check with your local dealer to find out if a specific vehicle was included.Google+
Car Problem Reports
GMC Sonoma Failed Wiper Motor Circuit Board May Cause Intermittent Wipers to Stop Working
GMC Sonoma Problem
Visitor, 1998 GMC Sonoma
Mine did the same thing and all that has to be done i the mother board of the windshield wipers has to be repaired. It cracks and that's when you wipers get temper mental.