Truck shuts off and is unable to idle; restarts after cool.

I have a 1996 Ford Expl Ltd, AWD, 4-door, V-8, 5.0 Liter Engine truck. I have 168,900 miles. I purchased the truck used - 1 years old - in 1997 with almost 50K miles on it.

Recently my truck shut off, could restart, but would only idle for seconds before shutting off again, if it was able to idle at all. All electrically parts worked on the truck, radio, lights, horn, gas hand, etc. It was almost as if gas wasn't getting to the engine. It's happened twice to date, but without notice. Both times it happened, the weather was warm and the truck had been driven that day for at least 2-3 hours. Once it cools down, the truck will start. However, you never know when this is going to happed as it does without warning. My friend said it was the ignition coil. However, I had the coil replaced and the truck did it again. Now what? Can you please help and advise what might be the problem? And is it serious? I keep my truck serviced and garaged kept.

Thanks,
Bambi240