Does it also do that little shake at take off? First thing to try is changing props. Do not use low noise props unless you have changed out to the P4Pro prop mounts. It would be a good idea to change to them anyhow for about $12. They are far superior and may solve your problem. All of my P4’s have the new mounts. The originals have springs that wear out.
What was that shake like? Was it wobbling before touch down or it was vibrating when already at the ground.
If the firs probably the cause is as described in post #6.
If the second - might be the problem with props fixation or they are out of balance. All this is easy to check and to solve out.