HP laptop automatically turning on and off on its own

Hello everyone, I'm in need of assistance with a perplexing issue. 

My HP Elitebook 840 laptop has started behaving erratically. Upon pressing the power button, it powers up and functions normally for a variable duration, ranging from 30 seconds to 10 minutes. Unexpectedly, it then abruptly shuts down, and subsequent attempts to turn it back on are unsuccessful. It remains off.

Strangely, the laptop spontaneously restarts at unpredictable intervals, sometimes after an hour and occasionally up to twelve hours later. The only indication of this is when the Windows welcome startup sound plays.

I am unable to provide the Windows 10 version number as the laptop shuts down before I can locate it. However, it has been consistently updated until this issue arose a few weeks ago.

Despite not overheating and with the fan working properly, the problem persists even after swapping the SSD with an identical clone. The battery has been ruled out as a cause. During a brief period when the laptop remained on, it was tested and found to be in good condition. This behavior occurs regardless of whether the laptop is connected to a power source.

Any advice or recommendations would be greatly appreciated.