System specs plz. Check your RAM sticks that tone didn't get knocked loose, if it's all the case fans, CPU fans etc. If it's the GPU fans only, boot into the OS and install the latest driver, usually I tell people to use an older one but the last 2 drivers have fixes for your edition GPU. So try the new driver first. Use the "factory reset" option when installing it.
I have the same issue with my RX 5700XT. The problem appeared on drivers version 21.2.2 (and still present on 21.2.3). On 20.11.2 looks like all work fine.
Sometimes I have the issue with one of my fans, sometimes with both. They can start to work on maximum speed randomly, but usually, it happens while playing even when I only just start the game and a temperature less than 50 degrees. Fans work on 100% ignoring any fan speed settings despite that, all monitoring programs show 0 rpm. And when fans start to work at full speed nothing can stop them. Neither PC reboot nor clean Windows reinstalling. They also work at full speed even in BIOS.
Only one thing helps for me - make uninstall the last driver through the DDU program, and after this instal/uninstall a few times 20.11.2 driver version. It's only one way to stop my fans. Any other methods do not work for me.
My PC specs:
AMD Ryzen 5 3600X
Radeon RX 5700 XT 8G Pulse
MSI B450 Gaming Plus Max
HyperX DDR4-3200 8GB 2x (but they works on 3466)
be quiet! Pure Power 11 700W