What could cause intermittent Trans. shift issues? on 2003 Dodge Durango

While cruising at highway speeds the Transmission will periodically shift down, then back up, as if on a steep hill. Does it wether the O/D is on, or off, same in cruise control. If I pull over and restart the engine, it solves this about 1/2 the time, but fuel economy has suffered since I developed this issue.
I continually monitor the fluid condition and level which is fine.
Is this an electrical malfunction? I have been scouring the archives here, and other sites but can't seem to discover much about this.
Thank you for the read. Your time and knowledge appreciated.

Asked by for the 2003 Dodge Durango