Radio/GPS shut off
 

I have a 2008 E350 and am experiencing an electrical issue. After driving for about an hour the air conditioning fan slows way down or sometimes shuts off. Then the radio/GPS shuts off and the A/C comes back on. But the radio/GPS stays off until manually powered back up. Once this starts it continues repeatedly. But once parked it hasn't happened again until a fairly long drive.
It has not occurred at the dealer and they find no codes so they can't do anything to fix it.
Has anyone experienced this or have any idea what could be happening?

I had a similar situation last year. The problem turned out to be the positive battery terminal was loose.

Thanks. It turned out that the positive battery terminal was loose. the dealer tightened it and says the problem is fixed..