ML 270 CDI Starting Problem
 

Our ML 270 CDI (2005) is perfect in every way except one.
It will not start if it has been stopped for 30 - 45 minutes after being running/warm. No problem if I want to start it before this elapsed time or after it. It seems like the engine must cool fully down before being able to restart.
One other maybe related thing - sometimes (for no apparant reason) it seems to briefly stall when motoring along at 100 to 140 KPH. This is accompanied by a orange exclamation mark display (!!!!). Then a few seconds more and the problem is gone.
These are intermittent faults - they have not shown up on the garage diagnostics.
What is the problem? Maybe air in the fuel line? Any simple fix?