I have a 2002 Volvo S60, and when started it up today it started having some kind of surges. Each surge would lightly rock the car, and the dash and headlights would dim and brighten each time. I drove the car around the block to see if it would stop, and when I got back to my house, the radio started shorting a bit. Needless to say, I took a different car out tonight. We replaced the alternator and battery about 2 1/2 years ago, so I'm not sure if it's that. Any idea what it could be?