noctua u14s

I have a PC with Ryzen 3950x CPU, Asus TUF B550 Gaming motherboard and Noctua U14S CPU cooler in a Fractal Meshify C case. The OS is Ubuntu 20.04. When the CPU is idle, the CPU temps are constantly changing between 34C and 58C. This is very annoying as it causes the fan to constantly speed up...