Fans cycling every few seconds from high speed to low speed

[itaroken_]

Hi,

My new PC that I built a few days ago has started having weird fan behaviours - the first 2 days it was not audibly changing like it is now. I downloaded MSI Afterburner and Riva Tuner to check out my temperatures and then it started doing the weird 5 second low power-high power fan cycle (and you can hear the fan noise go considerably higher, very noticeably). No matter what I'm doing on the PC it stays the same. I've tried putting the fans back to smart mode via the BIOS and uninstalling MSI Afterburner and Riva Tuner but it doesn't change anything. I'm convinced it's a software issue - what do you think it could be and how could I reset the fan curve? (I don't know much about fans, sorry)

Thanks, see specs below

 

B450M MSI TOMAHAWK MAX

Ryzen 5 3600 with stock heatsink

2 of Noctua NF-P12 redux 1700PWM

1 case fan from Fractal Design Meshify Mini 

PowerColor Red Devil 8GB 5700XT

16GB Corsair Vengeance 3600mhz

Seasonic Focus 650w 80+ Gold