Intermitant no start
 

Hi all , have a mysterious fault on my W140 se300 (1992 auto ), every now and again car wont start straight away after being driven 5-10km , allways starts first up , but when it happens its after a short initial drive. I have replaced fuel filter , and checked pump , it primes and runs . When the car runs its great , and no other probs . The 3 times its happened has been away from home , and haven't been able to check for spark , after trying to start 5/6 times and waiting awhile , it starts and of I go !. Ive rung the RAA the 3 times its happened ,but managed to start it everytime , before the mechanic arrived , they prob think im a serial pest ! , anyhow , anybody suggest where I can start to look ? , cheers.

Hi all , drove car again today starts first time like always , go to fast food drive through (10km ) and car starts idleing strangely while standing there waiting at window, try take of and car almost stalls , seems like missing , manage to drive off , then 30 seconds latter all ok , rest of the day ( stoped and started 3 times no probs ) , it only seems to appear on initial warm up , any ideas ?. , fuel regulator , bad crank sensor , idle control ? , cheers.