Q: car shaking randomly at various times

My car is randomly shaking at various times.

Sometimes it vibrates when in idle. This is regardless of if it's in Drive, Reverse or Park or if I shift to one of these gears once it's already shaking, at other times it doesn't do this.

Sometimes it shakes when driving. This happens either when I am slowing down to stop at a red light and then waiting for the green or when I am driving 40-60mph. If it's at those speeds it's mostly when trying to maintain the speed although twice when giving more gas to pickup more speed. At other times it won't shake at all.

Sometimes it shakes when reversing into a spot & other times it won't. I have so far checked the spark plugs, plug wires, ignition coils & air filter. All were good. I have changed the MAF sensor & fuel filter. I have used Chevron Techron Fuel System Concentrate Plus as instructed but the problem persists.

I currently do not see any check engine light.

Any help would be greatly appreciated.

Thanks!

My car has 196000 miles.
My car has an automatic transmission.