Ive got a new Mercedes E-Class 200 Kompressor purchased Jan '03

Firstly the radio sometimes just wont work, when you start the car, it lights up but there's no sound, you need to restart the engine before it works again

Second and most importantly, it stalls!!
It used to just stall when it was being reversed, now it stalls when it goes forward. This was from when the engine was idle waiting at a junction. The car had been running for 20 mins prior to the stall

Any ideas? Thanks