Hello. I've been facing this issue since December 2020.
MB: Asus x570 f gaming (bios - 4201 latest for today)
CPU: Ryzen 9 5900x (5950x) - stock frequencies
RAM: DDR4 3600MHz G.Skill Ripjaws V (F4-3600C18D-64GVK) (2x32Gb KIT) - 2666mhz in stock, no overclocking at all, Everything is in Auto in bios (double rank memory, Hynix chips)
GPU: RTX 2080 Ti 11gb
SSD: WD Black WDS200T3XHC 2ТБ
PSU: Silencer Mk III 850W
Cold boot takes up to 3-5 minutes(!!!). I press the button, see asus logo, then in ~5 minutes I see bios POST messages and loading normally. If I reset from windows/ubuntu - it goes fast (fastboot works). If I shutdown from windows/ubuntu - next power on is also fast. But If I press F2 or DEL button to go into BIOS settings, I have to wait another 5 minutes.
I've tried other RAM (unfortunately - on Hynix chips too) - same behaviour. Tried rams of 32gb and 16gb, tried to use only one ram and tried to use different slots - same thing.
I've tried another processor - 5900x and 5950x - same behaviour. Though ryzen of previous generations works fine! I've tried Ryzen 3 3xxx series - very fast even on cold boot.
I've tried to load withouth NVMe - same behaviour.
Does anybody know what's happening? Is it an issue with motherboard? Should buy a new one (probably not from Asus 🙂 ) or it can be ram issue?