Hi, I've bought the drone for a month about, and lately when hovering moves by itself, even though there is no wind.
You know how to help me?

Does it move up/down only or does it move side to side, forward and backward?   How high are you when this happens?

First thing I'd do is calibrate the IMU and then the compass.    If it only has trouble maintaining a constant height when you're just a few meters off the ground, the vision sensors might need calibrating.  See video below:

Any chance you inadvertently switched to atti mode? In that mode the drone sensors are off including gps. Only thing working autonomously is the attitude (normal flying position while in the air). In attitude mode the flying is done by pilot only.
The controller has a switch marking on, p, s, a, off. These are the control modes. Only the p mode is fully sensor enabled. Try to make sure first that the controller is switched to p mode.

Calibrate everything. The vision sensors, the IMU, (might as well do the compass at this point as well). That should solve any issues

Hi, I bought the DJI FPV drone about 3 month now. Lately when hovering moves by itself, even thought there is no wind. I do the IMU calibration and also the compass and it still and making a vibration strange noise, please DJI TEAM help me!!!

Are you sure the motors are spinning freely?  Are you sure the props are not chipped or bent?  In my experience, when you have a problem as you described and proper calibrations don't resolve it, you likely have a gyro stuck.  Disclaimer - I don't own an FPV.  Good luck.