Which model? There were a couple models that have been problem prone...or so I remember when I was working in a bay last year. I think the 6000 was coming back a lot.

The capacitors inside the deck itself could be going bad and unable to hold a charge as well as they did before, possibly drying up? Kind of a weird thing to happen, but possible.

How's the alternator on your car? battery?

...might be shot.