I have a '99 C5 and it will not start. It went dead at a tfc light and re-started...a week later it went dead again and re-started...the next week it went dead and I had to call a tow. I can start it with starter fluid, but it goes dead. The fuel pump seems to be running...I can hear it in the tank. No codes presently. I did install the CLB...the wheel was locking intermitently...it was a shot...no change. The starter spins, but it is getting no fuel.

 

Dont know if this will help but on my 02 when the ignition switch started to go out my car would die unexpectedly at different times ( on the highway, at a red light and so forth ). Once replaced I have had no more problems. It would also be hard to restart once it died. Hope I was of some help.

 

My 84 did exactly the same thing,died and restarted a few times and then wouldn't start 'til I changed the ECM. Have you checked for fuel pressure? Have you checked for spark? A failing spark module could also act that way. Good Luck!
Ron