pchopeless

When I start up or take my pc out of sleep mode, the monitor comes on for about a second, then goes off. The green power light is still on. If I swith the monitor off then on again, I see the screen again for a secind, then it goes black again. everything works in the background, i managed to reboot by switching the monitor on and off about 10 times so I could see where the cursor was but it didn't fix it. Please help