Was this vehicle a recent/used purchase, or one you've owned since new? And how many miles do you have on it?
Spark plugs should be changed about every 30k miles on this Jeep, but it's a quick DIY thing and uses basic copper plugs, so not expensive either. So it's possible if they hadn't been changed in a while, they needed it.
If it has the CVT automatic transmission (the automatic that you can +/- shift by pushing the shifter left or right), that needs to have a fluid/filter change probably every 60-75k miles to be safe...so if that hasn't been done, it'd be a good thing to do.
But the one thing that stands out to me is you say it isn't a problem until you get up to operating speeds, which makes me wonder could it be the thermostat? I've not replaced mine (2008 model, bought new w/136k miles now), BUT I learned recently that these vehicles have TWO thermostats. I forget the distinction, but one opens at a set temperature, and then a second one opens later. No idea if they're located together or opposite sides of the engine, but could be one of those is bad, which might explain why you don't have the problem until things warm up. If they haven't been done I'd suggest having them both checked.