On a routine restart, the computer power shuts off a few seconds after pressing start button.

[Bluemax36]

I was having a problem in my Firefox browser that I couldn't solve.  I closed the browser and shut the computer down.  When I pressed the start button to restart, the power would come on for a few seconds and then it would shut off.  I opened the computer thinking it might have been a temperature problem.  Both fans are working.  I cooled with an external fan, and that made no difference (it wasn't very hot, anyway).  After researching on line, I removed and replaced both RAM memory cards.  When I remove the power cord and reinsert it, the power comes on without me pressing the power switch, and then the power shuts off after a few seconds (nominally ten seconds).  Sometimes, not always, I can get the power to come on when pressing the power switch.  My guess is that there is a problem in the power switch.  I have not attempted to do anything with the switch.  The computer has operated well using an Ubuntu Linux Operating System for approximately two years.

[A4Apollo]

Hi! @Bluemax36, 

Have you tried checking with a different power chord?

Does your PC shut down while you are in BIOS?

It certainly sounds like an issue with the power switch. However, please find the reasons why your PC is shutting down randomly.

It could be overheating, due to a failed fan.
 
It could be "over-temperature", such that the motherboard is proactively shutting it down, to prevent a problem.
 
It could be a fault with the hardware: motherboard, the RAM, the CPU, or the power supply.

In this case, changing software is not going to help.

Also, Try performing a hard reset on your PC and check if it helps.

Many startup errors and other problems can be resolved by decreasing the amount of power stored in hardware components. Decreasing stored power is sometimes referred to as a "Hard Reset". Use the following steps to perform a hard reset on a computer:
If Windows is open, click Start and then Shutdown.
If Windows is not open and the computer has power, press and hold the power button on the computer until the computer shuts off.
With the power off, disconnect the power cord from the back of the computer.
With the power off and the power cord disconnected, press the power button on the computer for 5 seconds. The power light indicator on or near the power button might turn on briefly but then go out.
Reconnect the power cord and turn on the power.

If the issue persists please contact HP support for service options.

Contact HP support using this link. Click Here

Take Care! 🙂

Please click “Accept as Solution” if you feel my post solved your issue, it will help others find the solution.

Click the “Kudos, Thumbs Up" on the bottom right to say “Thanks” for helping!