Intermittent ignition issues.

What is your question?

Twice over the previous two weeks I have turned the key and every light appears and the car ignites but quickly fails to hold an idle. Later, the problem vanished and car works properly. Rather than wait for the next time I need to know what are the potential issues that need attention.

What makes this problem better or worse?

No clear reason for ignition failure

How long has your 2003 Mercedes-Benz E500 had this problem?

twice in the previous two weeks