PC pulsating humming noise.

[[TC]►Bez◄]

Hey guys, I've had this problem pop up at boot every 2 out of 10 boots. I'm not sure if its just caused by the components in the fans being cold or what, because its making loud pulsating humming tones. I'm not sure if its even is a fan because once it's finished humming it stops all together. It can go on for about 3 minutes then randomly stops and I don't have the problem while my rigs turned on. Could it just be cold?

Here's a video of the noise from this morning.





(The banging/knocking is me with my phone, don't worry about that.)

Anyone have any answers to as what it is? I've watched my CPU & GPU fan speeds as its happening and they do not change at all during this noise.

Many thanks!
-Bez