How do you fix overheating issues in a Jeep Grand Cherokee Laredo?

My jeep overheats when I'm at an idle. It
doesn't shake or feel like its going to die out
it runs as if all is okay. Once I drive on the
freeway or thru town with not much stop
and go my temp goes back to normal. My
air conditioner will blow warm air once the
car starts to overheat and then cool again
once the temp goes back down. I just
replaced my radiator, water pump, as well
as my top hose. I've burped the lines.
Tested my thermostat and all seems to be
fine. Please help me figure out what I'm
missing and need to replace.