did you drive through heavy rain?? I noticed this to be the #1 problem with my car and either a no start or it dying and being unable to restart...
if you drive through rain/leave the car parked outside, you could have moisture in a variety of places (as the distributor cap, ignition, relays, ect. are VERY exposed to moisture inherent in the 911 design). there's lots of helpful posts on here to protect against moisture on here, best of luck
andy