My Navi system cycles on and off frequently as I'm driving. Sometimes it will repeatedly cycle for several minutes. When it cycles back on the sytem starts up similar to when the car is first turned on. The diagnostic screens all show in the green. It seems there must be a short in the power somewhere. Any other ideas of what might cause this problem?

 

There's no short. Your DVD drive is dirty or dying. A cleaning disc will not work, you'll have to either get someone to take the drive apart and clean it or you'll have to replace the nav system. I had a similar problem and it's discussed somewhere else in here. Mine was caused by off-gassing of the plastic trim that clouded the lens.