jmague20,
Shutting down after a minute or two of on time can be difficult to diagnose with software or POST Cards. When the system resets there is not enough time to write or capture logs.
It is most likely one of two things. A bad or under powered Power Supply or a thermal issue.
On the POST Card, You may have to change the jumpers on the POST Card for that PC. The instructions on how to do that are on the packaging.
To fix the problem Make sure the CPU heatsink is properly attached and the thermal compound is evenly spread. If you have a spare power supply use it in place of the existing one. If not then disconnect the hard drive and any other high current Parts and see if the problem goes away.
-Fred