I finally managed to fix the issue.  I'll leave it here in case someone else encounters the same issue. For some reason the BIOS option "Attempt Legacy Boot" was set to Enabled, which caused this issue. Setting it to Disabled completely fixed it.
I posted an issue about a month ago about my problem: [URL]   Basically, as soon as I got my laptop, I switched the internal HDD for an SSD drive and re-installed Windows on it.  Most of the time (especially after a cold reset or power-off/on), the BIOS will boot into SupportAssist, perform a full check, find no issue, and turn off the laptop. If I interrupt it by pressing F2, going into the BIOS, and doing either Save&Reset or Discard&Reset, the laptop will reboot and boot the OS properly. If, after poweing up the laptop, I press F12, and pick the UEFI entry manually, it will boot the OS properly. I completely formatted the disk once more, and installed Linux only.  Exact same issue. From the discussion above, I assumed it was an issue with the SSD drive. Today I got an M.2 NVMe drive (Samsum 960 EVO), and re-installed Linux on it.  Exact same issue. I tried removing the previous 2.5." SSD drive.  Exact same issue.   In the BIOS, I disabled everything SupportAssist-related, and fiddled with most settings I thought could somehow affect this, but to no avail.   It is extreamly annoying, having to go through the BIOS or F12 every time I turn on my laptop. Any insight on the issue would be greatly appreciated. Jonathan
Laptop almost always booting into SupportAssist