The fact that it only overheats when your not moving really indicates a cooling fan issue.
Your truck is equipped with two cooling fans, 1 mounted to and driven by the waterpump. The second fan is electric, and mounted on the back of the radiator (if you peek in with a light you can see it). The electric fan is VERY loud. Loud enough to mostly drown out the engine noise at idle, and can easily be heard with the hood closed from several feet away.
I strongly suspect your having an issue with the electric fan. Diagnosis can be tricky without a scan tool to actuate the fan and test out the circuits.
Another common problem with Dakotas is the radiator cap.. The seal goes bad and allows coolant to be pushed out when the engine warms, but not drawn back in when it cools down.. This leads to an overfull jug (the overflow jug) and a low coolant level in the radiator. I would have the cap tested.
The 4.7 motor does not tolerate overheating very well, it doesn't have to get hot to many times before you wind up with warped cylinder heads, be very carefull not to let it overheat if possible.
I suggest having the electric cooling fan operation checked out as soon as you can, to prevent more serious engine damage. You should be OK at this point, as it doesn't overheat on you going down the road. While it's in have them pressure test that radiator cap.
I hope this helps, if you have any questions or need clarification don't hesitate to ask!