flashing dash and headlights

Update. 03 L200 W/57k. This just started happening. When the car is warmed up and the ign is turned on the headlights, dash, interior and taillights flash on and off. In addition, the gauges go dead for a moment. There is not pattern and it can occur any time the car is running whether parked or moving. It seems to occur at night or it may be that is when the car is most warmed up. Any help on where to start troubleshooting is greatly appreciated. Al