While doing some office cleaning, I accidentally discovered one of the features of my new X570-PRO:
as soon as I dusted off the keyboard the PC came to life.
Willing to disable such a feature I quickly found out the way and so I went to
BIOS > APM Configuration > Power On By PS/2 Keyboard,
but I found that the option was already disabled.
Moreover, I noticed that the system gets turned on by pressing any key, not just the listed ones (space bar...).
Is this a kind of malfunction or am I missing something?