Firstly, as stated above, check the power and the video cable - these are common problems and reasonably easy to fix.

Failing that, test the monitor on another machine. If it works correctly, then you know there is a problem with the output of your graphics card - it could be sending an off signal when it shouldn't, for instance.

However, if you have the same symptoms when it is hooked up to another machine then the monitor has an internal fault that can only really be solved by an engineer. Take it from somebody that's tried it - opening a monitor without knowing what you are doing and/or an electrical engineering degree will seldom lead to a positive outcome.