Monitor not showing anything

I'm no expert in computers,but I need help. We've had this monitor for a long time and it doesn't show anything these days,everything seems to be fine and the computer itself is on. When I turn off and then on the monitor,it shows a brief image and then goes black again,we've tried connecting the monitor to our laptop and it still shows a brief thing and then goes black. We want to know if this problem is because of the monitor itself,a cable or anything else.we don't have hdmi cable or anything else to try with other cables.any help or advice will be appreciated!