Car won't start unless the engine is cold...
 

My is250 is at 170k miles now and it only starts when the engine is cold. Once it starts, it drives normally, but I can't turn it back on after around 5 minutes of it being off. I have to wait until the engine is completely cold again in order for it to turn on. Anybody know how I can fix this?

When this happen next time, Open the Gas cap and close it again and see if that fixes the problem. Also check if the gas cap seal is in good shape. How old is the battery and when was the last time plugs were changed? I assume car cranks when hot but doesn't start?

Check your starter motor. Maybe it is on its way out. Mine was acting like this and found it to be a problem

So what exactly happens when you attempt to start the car when hot/warm/operating temp? Be specific. Does the starter attempt to turn over the engine, but the engine just doesn't fire?

Any CELs?

Replaced the starter and everything seems to work fine. A huge thanks to you all for helping!