I have a 05 Magnum with 2.7 liter engine. After car has been sitting for several hrs (happens every morning) lightning bolt comes on the dashboard and temp gage is not working. I cut car off and restart and all is good with gage and no lightning bolt.

This has happen twice .....driving down the road and temp is fine and all of sudden temp spikes and car runs hot. I pull over and cut car off wait a couple of min then start the car and temp goes down. No more issues after cooling down.

My question is are these problems related or do I have have two seperate problems. I'm thinking thermostat and sending unit? HELP!