Mercedes 320 Engine not turning over?

As i was driving my engine started to lose power as i was driving up hill and ultimately came to a stop, i figured i must have ran out of petrol as it was closeish to the empty mark, i tried to start the car again and it started up but when i moved the car into drive it would stall, i eventually got towed to a garage and put some fuel in when i tried stating the car there was nothing not even an attempt to turn over.

havs anybody experienced this or know what the problem could be?

the model is below:

Mercedes Benz CLK 320 Sport 1999