>>3729546Sony camera's do (at least my A7RIV does) this once a month.
If you own one you can notice this happening if you power off the camera. The screen will go off, but you hear the shutter curtain close.
Then a few seconds later the curtain opens again and you finally hear the sensor/steadyshot lock into its locked position.
This happens once a month and is for automatically getting a noise profile of the sensor to improve sensor accuracy.
Maybe other cameras do this too, but I've never noticed it
