1996 Volvo 850 Electrical Problem Starting the Car

1. Something is draining my battery. No lights or radio left on. Battery dead. Not even a dashboard light comes on after several days without driving.

2. Even with a fully charged battery, once a week, when I try to start the car, the full dashboard of red warning lights comes on, I turn the key to start the car and nothing happens. The engine doesn't turn over. The key is turned all the way but nothing. Then after about 5 - 10 minutes, I turn the key and the car starts like nothing was wrong. Happens randomly.