Is that supposed to happen? Why does it first look like it's trying to spin but failing?
Probably because the PC powers up with the motherboard's fan controller set to full-power by default then gets reset by the BIOS during POST before the fan gets a chance to start spinning until the BIOS gets around to re-programming the fan controller's parameters after which the fan starts for real.
When I set my BIOS to Quiet profile, my CPU fan sometimes fails to start because the fan PWM output is too low. It eventually spins up after the CPU warms up during Windows boot.
I'm not worried about the fan not spinning since my CPU does not even reach 70C core temperature under load with the fan disconnected.