Why is my phone suddenly making radio noises when it's turned off?

So, this just started recently. Yesterday to be exact, I've woken up a few times because my samsung a11 phone is suddenly making like radio wave sounds/ or like the sound the tv makes when it lost its signal? Im not rly sure how to describe it. It didn't happen the whole day and I totally forgot about it but then it happened again when I placed my phone down and I suddenly heared it! Is this a new bug or something?

Edit: Just to clarify it's not shut off/down its just when you press the powee button and it sleeps? Sorry im not rly sure what terminology to use