I have a peculiar problem with my '99 New Beetle. The battery has lost charge several times. Also, the radio will be dead the first time I drive the car on a particular day, then work just fine that evening. There is nothing left plugged in or turned on. I have checked all the lamps and switches inthe car. I amstumped! It will start right up when I get a jump. Run just fine for a few days, then go dead mysteriously. Any ideas?