I am not an M-B expert, but figured that my girlfriend's recent issues with her 96 C280 might be of help to you. It led me to post here yesterday, and the support/info I received helped to prepare me to deal with the dealer on a "Goodwill Warranty" repair. Here's what I know -

(1) Her C280 had the same issue as you - random no-starts. This seemed to fixed by taking off the gas cap (a fix I learned from my old 190E - some kind of vapor lock). Or so I thought...

(2) After tailgating with the C280's radio blaring, the battery died. Thus it was concluded the (1) may have been due to the battery more than the vapor...

(3) Finally, the car in for a 75K service was diagnosed with a badly deteriorated wiring harness - priced at $1000 including parts & labor. After some struggle, the repair was covered under a program discussed on message boards here.

I hope this helps you.