Engine stumble it might stumble again after a few seconds?

My car runs fine, except it idle. I have an occasional stumble, acceleration seems fine. When I decelerate the engine, RPMs drop below 500 at times, but never dies. At a traffic light, it will be idling fine, and all the sudden I get a stumble it might stumble again after a few seconds, or maybe a minute. I have no codes. If I slow down from 30 mph and try to turn in a parking lot, it may stumble, the power steering will not perform very well, when that happens.
I don’t know if it’s O2 sensors or maf sensor, or coil packs, or spark plugs, as I have purchased this vehicle used with 119,000 miles on it. I just don’t want to randomly start replacing parts. Any suggestions on where to start looking?
Also at idle in drive and I cycle the AC on and off, it sometimes will stumble. But not every time.
On the highway it performs very well, there are times when I may be driving between 40 and 60 miles an hour, and I lightly step on the gas, to pass, the engines seems flat, or possibly the transmission, is that culprit. But, in general the car performs very well.