Does anyone know what would make it over heat by sitting idle for a few minutes then cool back down when moving.

Plugged radiator.

Bad fan cluth

bad thermo stat.

Typically when people report this, they first flush the rad a bunch. Then they switch out the thermostat. This usually does nothing.

The thing that fixes the problem is replacing the radiator.

If you have over 150k on the orginal Rad, I would bet that is what your problem is.

Also I would search a bit too on how to check for a bad fan cluth first.

It is most likely one of the three things Ryan mentioned. Good luck.