Monitor displays breifly then goes to blank screen. Hi, Whenever I turn on my monitor it displays

Question

Hi, Whenever I turn on my monitor it displays the computers output briefly (~half a second) before going blank. I have tried the monitor on two other computers with the same result so it is definetaly not a computer problem. The power light on the front of the monitor stays green when the screen goes blank. Whenever I turn the power off and back on again the exact same thing happens.Help please!!