How can I fix my monitor? HELP ASAP?

My monitor keeps turning itself off, and it's driving me crazy! I'll turn it back on, it stays from a few seconds to a minute or so, then off again. Does anyone have solutions to this problem? I have Windows 98 iof that helps. The computer is an e-Machine, and monitor NEC MultiSync 3V

Thank you so much!
Linda
Stormygal5155@Aol.com