with the key in the on position the radio/cd works great,however after i start the car the antenna will retract and the music stops....It will come on again once I cut the key off and on but shortly goes out again.there is no other issues with the car or ignition switch and key

 

Is the radio unit stock or aftermarket?

Start off checking the wiring that goes to the radio

1995 Mercedes E300D Car Stereo Wire Schematic