It is either a hardware or software issue.
If moving the screen, tapping it or things of that sort stop or change the flickering then it is probably a hardware issue. Could be anything from a loose or dirty cable, failing inverter, failing back-light, failing lcd.
It could also be something as simple drivers that updated and need to be rolled back, or a incorrect refresh rate.
The first thing I would recommend is to go over to google type in the make and model of your laptop and "flickering screen" Problems of this sort usually aren't isolated so it should be documented somewhere on the web.
