When I turn the key in my new (5 days) 98 E320, it readily ignites and then stops as if I turned the key off. This first only happened if the engine was warm but now happens any time. If I gently depress the accelerator for about 2 seconds during and after I turn the key, the engine stays on.

The car appears to be meticulously maintained and I haven't done a tune-up yet. Any constructive input would be greatly appreciated.

Thanks in advance
Mike

 

Does it splutter before it turns off? When you turn on the car, try to keep the revs at about 1500-2000rpm for about 2 seconds, then see if it turns off. If it does, then try again for longer or at higher revs.

 

Looks like a crankshaft position sensor issue. First check for any code. Check Benzworld.org. This have been covered in several threads in that forum. There is also a DIY, if your are into it.