uusually when the 5.7L do that is the egr valve sticking same thing happened on my 06 ram and oh by the way been working on them for over 16 years at the same dealer
I was thinking the same thing but then you'd expect to get a code when the EG sensor sees a rich exhaust at idle if the valve was stuck open. Id go over all the connectors on the ignition and fuel rails first, also when was the last time the fuel filter was changed. Plugs when running, crap falls to the bottom of filter when shutdown then engine starts right back up again.