When my 99 ML320 is cold it starts and runs perfectly. When it has run
a few minutes it will suddenly shut down  and I have to let it cool
down for ten minutes or so until it starts again. It turns over fine
but will not fire. It will sometimes drive fine for a few miles but
when I stop and turn off the engine it will not start. After it cools
down it starts ok. The "check engine" light does not come on. I took
it to a local mechanic but he can't get it to repeat the behaviour.
Any ideas as to what is going on would be very appreciated.
Terry