WE HAVE A 1986 300SDL AND THERE ARE SOME STRANGE THINGS HAPPENING THAT I DO NOT UNDERSTAND. HERE'S THE PROBLEM:

WHEN THE IGNITION SWITCH IS FIRST TURNED "ON", THE LEFT AND RIGHT SIGNAL ARROWS WILL COME ON TOGETHER AND THE CAR LIGHTS WILL DIM, THE SPEEDOMETER AND OIL GAUGE WILL GO TO ZERO AND ALL DASHBOARD LIGHTS WILL GO OUT FOR A BRIEF PERIOD (TENS OF SECONDS TO A FEW MINUTES). THE CAR ENGINE WILL CONTINUE TO RUN FINE DURING THESE EPISODES. AFTER THE PROBLEM CLEARS ITSELF, EVERY THING WORKS FINE. THIS EFFECT IS TRULY APERIODIC AND IS NOT PREDICTABLE. HELP!

THE NEXT PROBLEM INVOLVING THE DASHBOARD CONTROLS IS ALSO WEIRD. IF I HAVE LESS THAN A FULL TANK OF GAS, THE GAUGE WILL BOUNCE BACK AND FORTH BETWEEN WHAT'S ACTUALLY IN THE TANK AND FULL FOR A SHORT PERIOD AND THEN STABILIZE. THIS MAKES IT DIFFICULT TO KNOW HOW MUCH FUEL I ACTUALLY HAVE IN THE CAR. TO MAKE MATTERS WORSE, THE TEMPERATURE GAUGE ALSO BOUNCES UP AND DOWN AND INDICATES THAT THE CAR IS OVER-HEATING WHEN I KNOW IT'S NOT. IF THE CAR IS DRIVEN FOR A MINUTE OR TWO, BOTH GAUGES GO TO THE NORMAL POSITION.
THE OIL PRESSURE GAUGE INDICATION IS NORMAL DURING THESE EPISODES. WHAT DO YOU THINK IS HAPPENING?