[camcojb]

I would think it's an issue with the ecm not getting an rpm signal. Not sure why it only does it after a cool down. Have you looked at the battery voltage when cranking in this condition? If it has any kind of heat soak issue or similar and the volts are dropping to 10 volts or so it will cause what you're seeing. Had this on a friends car and a new battery with more cranking amps fixed it. Thing is the engine seemed to spin over fine, but looking at the voltage when cranking told us what was going on.