Most Class A motorhomes do not have this problem or only have it on certain campsites.

First make sure each jack is firmly down, if you can make the jack pad rock on any of them you need to put that one down more. This happens to us some campsites, the ground settles after we set up or the jack was sitting on a rock that held it up a bit high. I use a metal bar to see if the pad will rock, even a 32nd of an inch can be felt inside.   With some rigid jackpads you might need to use a thin piece of plastic between the pad and ground to see if there are any gaps, a plastic knife should work.

If that doesn't fix it the next step is to have someone walk around inside and check each of your jacks with a flashlight to see if the jack is sinking in the ground or the jack is moving up and down on its own. If it is moving on its own, the jack is malfunctioning since they should be rigid when down.

If you are on ground that gives, dirt and sometimes gravel, we will get some rocking since the ground is compressing and releasing under the jacks and tires. Just like a mattress. We have large jackpads, about 10" squares, but that is not always enough. You can try putting out 2 foot x 2 foot boards under the jacks, but they need to be thick enough to not flex. Chop up an 4x8 piece of 3/4" or thicker plywood and put two of them under each of your four jacks. This will spread out the weight of your motorhome over a much larger surface area.