Laptop performance slowing down, or the laptop is shutting off completely because the laptop is trying to protect itself from damage caused by an excessive heat build-up. ... There are times when a laptop will turn off because of a virus or malware, hardware or software problems/conflicts as well.
1- Dirty Fan/Overheating ;Please see previous Post
2- Hardware Failure;
Another common reason for a random shut down of your computer is a hardware component failure, which is not unheard of, especially on computers that have been refurbished. If you’ve recently “added any new hardware” this is the time to remove it to see if the shut-down issue goes away.
The hardware to check first are as follows: RAM, CPU, your motherboard, power supply and your video card.
Also note any patterns of beeps or flashes, and refer to the manufactures webpage.
3- Wrong Charger Voltage;
There is another major cause for the laptops to turn off randomly that is the faulty power supply. It is the most dangerous problem as it can cause severe problems to your laptop like your laptop can go dead due to the faulty power supply.
Because the value of current decrease and also increases, so it greatly damages the battery and laptop itself. If you are having the same problem, it is recommended for you to change your power supply as soon as possible.
4- VGC Driver Crash;
If you’ve tinkered with your operating system or have changed drivers on your computer, this too can be troublesome, especially if you’re playing around with BIOS. A driver crash can always completely shut down a computer. AMD display drivers or the AMD Catalyst Suite are two common display drivers that have been known to crash.
To determine the driver that crashed, when your computer starts back up look to see if you have any dump files at the top of the crash posts. These files will tell you everything you need to know.
Battery problem is another major reason for random shutdown of laptop. This problem usually occurs after a long use age of laptops, or excessive charging. If your laptop shuts down randomly, test your battery if it’s working well or not. If it isn’t, you really need to buy a new battery. Make sure the battery has the same amperes the laptop requires, otherwise your laptop might have problems while working.
6- Computer Virus;
Please check this Post