2007 Dodge Durango fluctuating RPM's !

I have the strangest thing happening while in park or in gear. When idled at a red light, in drive and foot on the brake the RPM needle jumps around. Normal idle may be at 1000RPM but then it jumps to 1500 then back down. It also does this while driving. It doesn't matter the speed I'm traveling either. It does it at 40mph or 70mph. I know the needle will move when speeding up to pass or slowing down, but it does it even when I'm at a steady 55mph or 70MPH, even on cruise control. The RPM's will jump as high as 2500 then level back off again. It even does it when I use my remote start in the AM, I can hear the racing up and settling down before I even get in the vehicle. Sometimes it doesn't happen at all but the next trip out it starts again. I have no warning lights on ever. I change the oil about every 4000 miles and I recently had a transmission flush. It was doing it before the flush then stopped for about a week then started again. My regular maintence garage is actually a tire shop and doesn't do this type of work. They referred me to a specialty shop but I at least want to go in there without being totally ignorant to what the problem could be. Thanks in advance for your help.