My Desktop asks to close all programs

Hello friends,
I am using HP – Pavilion Slimline Desktop – 4GB with Windows 8.1 (64 bit) operating system in it. It was working fine so far.
From today it started getting strange issue. When I start my computer and open few applications (not many) all of sudden it is showing a message to close all programs to shut down the system. When I close all programs it is being shut down immediately. If I restart the system it will again show the same message.
What is the issue with my PC? In summer here the room gets heated and the Air Condition is not working. Is this a problem? How can I rectify this issue? Please advise. Kind regards!
