I have a 1999 E320 4-matic wagon (124k miles) that has provided very reliable service until this past week, when we had a heat wave.  I had driven it about 8 miles to a store and parked it in a hot (103 deg) parking lot.  When I came out 30 minutes later it wouldn't start.  After several attempts and about 10 minutes, it started and I drove it home without incident (no CEL showing).  The next day, also very hot, I drove it 5 miles to the post office.  Once again, when I came out after 15 minutes, it wouldn't start.  After several attempts, and 20 minutes, it started, so I tried to get it home.  This time it stopped after 3 miles, so I had to be towed home.  Now it starts fine (when cold), and I'm preparing to dig into it to find the "heat" problem.  I first pulled the connector off the crankshaft position sender and hit the starter.  It replicated exactly what had happened when I tried to start it hot.  I'd appreciate any thoughts on similar experiences, the CPS, and any other likely candidates. Thanks.