This happened a year ago. We got it running after a few minutes, and had the fuel filter changed before continuing on the highway again. It ran fine for the remaining 2 hours of the trip. I looked online and saw this as an issue, but no one knows why. It was suggested to take a break after 2 hours, and that has worked until 2 days ago, when it stalled an hour after the break, then restarted after some time and made it the next 1 1/2 hours home no problem. Each time it stalled, the air temp had been in the high 90’s.
These symptoms are typical of an ignition related component becoming sensitive to heat, and no longer able to tolerate the temp under the hood.
Do you have and fault codes stored? .
Could be a coil breaking down in the heat. Next time it does this immediately check to see if you have fire going to the plugs.