I had a similar issue.... After a bump start it never showed up again.

 

I just experienced a similar situation. I went up to Buttonwillow for a open test day. Did three sessions, car ran perfect. Went to start it for session number four and nothing, engine does not turn over gauge lights are on and everything works. Got a bump start, loaded the car and drove the 3 hours home. Shut it off and tried starting it and same thing. This morning I went to check it out and it started just fine. Checked the connections at the battery and starter. Battery is one year old. '86 911 BTW. Thoughts? I really don't like problems that fix themselves

 

Sorry I just realized I was on the 993 Forum

 

Could it be a dead spot in alternator? move it a little bit and it will stat. Stab in the dark.