engine starts to get hot before fans turn on to cool

The problem with this problem is that it only start to get hot when I'm sitting idle in my car and it doesn't do it all the time it. Its a random and I never know when it's gonna happen. Took it in to Dodge and of course they didn't see anything so until they can see the car getting hot before the fan kicks on they won't do anything to fix it. Its super frustrating since its a brand new car and I only got a brand New car to get away from the problems I was having with my last one. Anywya the finance company refuses to finalize paperwork and fund the vehicle until the car is working properly so kinda a scrappy situation.