1999 Catera. runs and starts fine during and after local trips (<20 miles). any trip over 25 miles at highway speeds results in sporadic starts. even after the car sits for over an hour. sometimes starts, then dies. after a few hours, starts and runs fine. what gives???
It could be a ignition control module heating up and then shutting down the engine. Then as the module cools the engine will run again until it heats up.
The only way to be sure is to have a shop check it out while the car does not run.