Mac mini starting itself when power is applied Having a weird issue with a Mac mini.

At the end of the day, I perform a full shutdown.  The main power is then turned off.

When the main power is turned back on again, the Mac mini is automatically turning itself on and starting up. I don't want it to do this.

Under the Energy Saver settings in System Preferences, start automatically after a power failure is unchecked. There is also nothing in the Schedule that would cause the machine to turn on.

Any ideas why my Mac won't stay off when the main power is reapplied?

EDIT - pmset -g output

Active Profiles:
AC Power        -1*
Currently in use:
hibernatemode        0
womp                 0
networkoversleep     0
sleep                20
Sleep On Power Button 1
ttyskeepawake        1
hibernatefile        /var/vm/sleepimage
autorestart          0
disksleep            10
displaysleep         20


EDIT 2

If I understand correctly, I will be resetting the SMC every day because the main power is removed from the machine. As per; https://support.apple.com/en-gb/HT201295

Could the fact that the SMC is being reset make the machine power on the next time main power is applied?
Have you tried removing any usb such as external hard drives? That's probably the issue