I have the same problem with you.
R5 1600, MSI B350M, 8GB DDR4 2400MHz
It takes approx. 30s to show the bios screen when I switch on......
Then start the windows for another 30s
But I have already updated the bios version to the lastest.
I don't know why, can it be fixed?
I did so. System disk made in GPT. Switched BIOS setting from LEGACY to UEFI (boot settings). A little better.
Unfortunately after reinstalling the system. I get a clock watchdog timeout message and PC freze.