Why does my laptop keep restarting after shutting down?

Question

laptops

HP 8460P
Or rather, not even a reboot, but an autostart. Those. with a software shutdown, with a hardware shutdown, with a power connection (battery or network - no difference) - a couple of seconds and the laptop starts.
This is definitely not related to the OS - the problem was also observed on a blank disk.
It seems to be similar to problems with the BIOS, but I turned off everything there that is somehow connected with "wake up".
Still, by typing, a method was found that can turn off the laptop without disconnecting the power supply - holding the Power button. Those. as if hardware problems are excluded (well, such as sticking the shutdown button).
The main "suspect" is sort of like a BIOS, but I rummaged through it all. Plus, the latest version is also worth it - it’s not so easy to roll back to some other one now.
In which direction to dig?