In the last week or so I have noticed that my '08 base GP (3800 III, NA) idles roughly only after the car has warmed up and when the A/C is not on. The RPMs are at about 600-700 when this happens. When the car is cold or the A/C is on the RPMs are more like 900-1100 and it's very smooth.

Also, this may be unrelated, when driving down the road the car has some hiccups/hesitation at about 35mph and 1100-1200 RPMs. When accelerating it is not noticeable at all. This only seems to happen when I'm maintaining that speed & RPM combo. I drive so aggressively and fast that I rarely experience it. It does feel very similar to what my wife's old '99 GP used to do at around the same speed and RPM. She never noticed it and my '98 GP didn't do it, so I never investigated the problem. Her car still ran fine for many years right up to when we traded it in.

These things wouldn't bother me at all on our older 100k+ mile GPs, but this car is 3 years old and has 42,000 miles on it. So, I'd like to sort it out. I'm thinking that the first problem may be related to the idle air controller. I'm afraid the second problem would be transmission related, but maybe something to do with the fuel delivery. It's really hard to tell if it's the engine or the tranny doing it.

This car has no mods (yet) and even has a stock air filter still. I'm fairly busy with a 2-month old and 1.5-year old, as well as, building a new 2-car garage, so any help pointing me in the right direction will save me precious time and be very appreciated.
Thanks for any help,
Doug

If it does it in park I'd rule out the tranny. Put a code reader on it see if any codes are pending

Could be a TB sensor. Maybe the MAF or IAC.