Is it a laptop? Usually these are set up to try to conserve the battery.
Check your settings under control panel/power options.
If you don't use your keyboard or mouse, it times how long this "inactivity"
continues, and may be set to hibernate/standby/blank screen etc.
Some laptops have their own setup program for this, instead of using the
control panel. Many have an option to temporarily put it into a mode called
something like "presentation", where it will not shut anything down even if
there is no activity.
|my pc shuts down when i'm trying to read something and i'm
|not using the keyboard or mouse