Audi wants to rest!

I have a wonderful to drive, 1976 Audi 100 ls with the CDI fuel injection system.

The car starts easily when cold and runs like it owns the road beneath it, hates the right lane, etc. It doesn’t matter how long the trip, or how long it has been running. When I shut the engine down, it will not start for a couple of hours. I have originally thought it was the coil getting hot, but drove 12 hours, 600 miles without shutting down. I thought it might be air getting into the fuel system somehow, but ??? How can I drive it for start and stop and start trips? Suggestions???

Air compresses a lot more than fuel. Have the fuel pressure measured to see if it is low. If the pressure is OK, it’s hard for me to imagine it’s air in the fuel line.