HP Elitebook randomly rebooting

[RaiderX]

I have bought a HP laptop cheap that was sold as spares/repair and I am trying to fix it but I've hit a bit of a wall.

The laptop is a HP Elitebook 845 G8, Ryzen 3 Pro 5450u.
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The issue with the laptop is that it will randomly reboot for no apparent reason, it doesn't even blue screen, it just goes black then the laptop tries to boot again. It is more prominent when the laptop is plugged in but does still occasionally happen when running on the battery.

So far I have tried replacing the RAM, replacing the SSD, repasting the CPU. I do not believe the issue to be thermals as I have run stress tests and it has not happened, but just sitting idle on the desktop it will randomly happen, and the fan does spin up when under load.

HP Diagnostics tools have all reported no issues, so beyond replacing the motherboard I'm kinda stuck on what I can try next.

 

[radderfire]

Just a guess, but could it be related to power delivery in some way? Maybe the way the computer manages power supply between plugged in to the mains and battery. Maybe the battery is involved in someway, even when the computer is plugged in. Possibly think about whether a faulty battery could be causing this??