2003 Mercedes-Benz S430 4MATIC Question: What causes an engine to seize?

While driving my car the engine stopped; Instrument panel lit up; Headlight shut off. I was able to coast to the shoulder while still in drive. Once in park, I waited 15 minutes before trying to start the car. the starter clicked, that's all. The battery was fine, I used my hazards for about 50 minutes waiting for the Tow truck.