Sometimes laptop shuts down immediately after starting to boot

Hi, I have HP Zbook 15 laptop (kinda old, bought in 2014). It has a factory configuration plus additional SSD on the M2 slot, which I use for my OS.

Recently it developed a strange bug. Occasionally, when I turn it on after either a full shut down or a hibernation, it would start boot up sequence, but shutdown after only a second, not even loading the BIOS. As a result, no error log is generated to check what might be the problem. And after that, if you wait a few seconds and boot up again - it starts normally as nothing happened… Usually just waiting a few sec is enough, although a few times I had to wait more for some reason.

I first thought it could be battery, but I had it occur without battery too. It has happened both after I left the laptop plugged in and after I disconnected it and took it with me elsewhere. Also, as it is kinda hard to reproduce, so it is difficult to analyse. Any idea as to what might cause this?