[1] download a program called Aida 32, when people ask you for specific parts and manufacturer names of your computer bits, use that program to show us.
[2] What temperature is your computer running at when it starts to restart.?
free temp programs will reveal it if your system does not have built in ones.
check your bios settings to see if it shuts down at a given temperature.
[3] Are you playing games and it shuts down?
What commonly is running when it shuts down.
Have you installed or changed anything recently after it started happening.?
[4] Please define more about what this "Installed" blue screen says