Why can't I see my screen image?

I Have a Samsung DLP Projection Tv (model: HLT6187SAX/XAA). I am having trouble getting a image . TV keeps restarting to a black screen? At times I am able to get an image to appear If its been a while since I used the Tv But most of the time the image is black ...with the power light on? Anyone have any clue how to fix this or what pieces are needed ?