I have a 1997 GMC 1500. It well be running fine and just die. It has done it going down the food and sitting idling. Sometimes it starts right back up.
Try changing out your Engine Coolant Temp sensor. If that doesn't cure it, try cleaning or replacing your IAC valve. It wouldn't hurt to get a can of MAF sensor cleaner and do that also. https://www.youtube.com/watch?v=_TO7ZC5N-aA