From time to time the computer will go slow and sometimes the computer will restart or shutdown by it-self.
In order to avoid that, here are somethings we usually do...
We sometimes open our computers not for work nor fun, but, we open it for Maintenance
In Software Maintenance. We do Defrag for the file fragments to be in the same place. Check-Disk to see if there are some errors on our files, and sometimes checking to see if there are some errors in the Registry by the use of some third-party software. We also remove some programs that we don't use because it only consumes space in the Hard-Drive and in some cases makes the computer slower. if you have an Anti-Virus and Internet, make sure that it as always updated at least every week.
In Hardware Maintenance. We only do a simple thing. Taking off the parts or hardware and blowing it in some air compressors so that the dirt is not stuck in the places where heat is being generated like the heat-sink of the processor and some other places inside the computer. If there is too much dirt, chances are your computer will over-heat and in most cases that is the cause of a Computer restart or Computer shutdown by itself.