Why can there be a delay before loading the BIOS 15-20 seconds?

Question

Iron

I turn on the PC, the delay is 15-20 seconds and the current then I see the logo and then loads the OS.
There is a suspicion that the PSU is not suitable, although at 650 watts.
Proc i7-6800K
Mother X99-E
PSU hp 650 g14s

Answer 1

Are there light bulbs meme ok on the motherboard by any chance?
The motherboard can each time check at what maximum frequency the RAM can operate, in this case the mem ok light will be on during the dullness.

Answer 2

It polls the hard drive (or ssd) or DVD drive for a long time, for the sake of experiment you can turn them off and make sure that the BIOS loads faster, and then connect the devices one by one, thereby you will find what is causing it to load so long

Answer 3

In addition to the above, let me remind you that BEFORE the main BIOS boot, all devices that have their own BIOS are loaded (or rather boot loaders of the start record) and I can not be distracted by displaying information on the screen.