Hi Gilbert,

There's a lot of factors that may cause to computer shutdown unexpectedly. Below are the things that may cause this issue.

Computer turns off without warning

Tip: This document is for computers that turn off and remain off after an extended period of use. It is not for computers that turn back on (restart),computers that shut off immediately upon powering up, or computers that do not turn on at all.
Caution: Some of the steps below require you to work inside your computer. Before opening your case, be aware of the dangers of ESD.

Heat related issue

Most computers today are designed to turn off automatically if any of its inner components overheat. Often, heat related issues occur when the computer is working hard, e.g. playing a graphically intense computer game.
Start by verifying the fan on the power supply is working by examining the back of the computer. The fan should be moving quickly and smoothly. All other fans in the computer require you to open your case to inspect them. Once you have access to the inside of your machine, examine the processor (heat sink), video card, and case fans. If you have heard any abnormal noises coming from your computer, such as a high squealing sound, it could be an indication of a fan malfunction.
If you find that the fan in the power supply is not working correctly or at all, and the power supply is very hot to the touch, you may need to replace the power supply. An overheating power supply, due to a malfunctioning fan, can cause a computer to shut off unexpectedly. Continuing to use the faulty power supply can result in damage to the computer and should be replaced immediately.
Note: If your issues are on a laptop, we do not suggest opening the computer. Instead, verify the fan on the side of the computer is working and blowing out hot air. Also, with a laptop, you may want to invest in a cooler pad to help lower its running temperature.
Tip: Working on the interior of your machine provides an opportune time to clean the inside. Dust, dirt, hair, and other trapped debris can prevent proper air flow, which may lead to overheating.
Tip: If your BIOS monitors the RPM of the fans, enter the BIOS and make sure the BIOS does not report any errors. Software utilities such as SpeedFan can also be used to help monitor fans in your computer.
Tip: Check the processor heat sink to make sure it is properly seated and has thecorrect amount of thermal compound.
Caution: If you do remove the processor heat sink, thermal compound should be cleaned off and new thermal compound should be applied.

• Is there a way to tell how hot my CPU is running?
• What should be the temperature of my processor?

Hardware related issues

Tip: Before attempting to remove any hardware, rule out hardware conflicts bychecking Device Manager for errors.
Any failing hardware component in your computer could cause your computer to unexpectedly turn off without warning. If you have recently added any new hardware, remove it from the computer to make sure it is not the cause of the problem.
If you have not recently installed any new hardware into the computer, the next best solution is to systematically remove non-essential hardware. For example, remove your modem, network card, sound card, and any other expansion cards that are not needed for your computer to operate. Running the computer without these cards may help diagnose your issue.

Problem with UPS or surge protector

Make sure any surge protector or Uninterruptible Power Supply (UPS) is not the cause of your problem by connecting the computer directly to the power outlet on the wall. Also, if you have a UPS that connects a USB cable to the computer to manage power saving features, make sure it is also disconnected.
If this resolves your problem, you may have a defective surge protector or UPS. In the case of the UPS, there may be other issues, such as a UPS overload or UPS drivers, reporting bad power situations that cause your computer to shutdown. Make sure there are not too many devices connected to your UPS and that it has the latest software updates.

Computer virus

Your computer may be infected with a virus or other malware that is designed to shut down your computer upon certain conditions. If your computer seems to be turning off when executing a certain program at specific times of the day, it could be infected.
If you believe your computer may be infected with a virus, download a free scanner. If you already have one installed, make sure your virus scanner definitions are up-to-date, then run a full scan.

Issue with operating system

If after following each of the above recommendations your computer still continues to shut off, it is possible you are experiencing a problem at the operating system level. To see if this is the case, try the steps below.

1. Reboot the computer and enter CMOS setup as the computer is booting.
2. After you have loaded the computer in CMOS setup, let the computer sit.

If the computer does not turn off after staying idle in CMOS, your operating system installation may be corrupt. We recommended that you erase everything and reinstall Microsoft Windows.

Other failing hardware

If your computer turns off abnormally during (or just after) installation of your operating system, it is likely that other hardware is failing in the computer. Often, the hardware causing the issue will be either the RAM, CPU, Motherboard, Power Supply, or Video card, in that order.

I hope this information gives clarity to this matter of issue.

Regards,


Ryan

Hi Gilbert,

If your PC is unexpectedly getting shut down, it's almost certainly overheated. The PC, which monitors the temperature of the CPU, is protecting it's delicate circuits from the ravages of heat. 

This can happen for several reasons like your computer’s case may be full of dust, a fan may have failed, or something may be blocking your computer’s vents.

You can try the below steps in order to make it work properly:

• Make sure nothing is blocking the PC's air vents.
• Unplug the PC and open it up. Use a can of compressed air to remove dust, especially around the fans and vents.
• While the PC is open, note the position of the internal cables. Are any of them blocking vents or air flow?
• Plug in the PC--while it's still open--and boot it to make sure that all the fans run properly. If one isn't spinning, try to find out and fix what's blocking it.
• Ensure Proper Ventilation: Put the computer in a location where it can properly ventilate itself. If it’s a desktop, don’t push the case up against a wall so that the computer’s vents become blocked or leave it near a radiator or heating vent. If it’s a laptop, be careful to not block its air vents, particularly when doing something demanding.

I hope this helps.

Regards,
Lokesh