This may be caused by many factors, but in general can be described as unstable brightness, and happens. When you can see light gradations changing too harshly, instead of in a subtle and smooth manner, flicker becomes noticeable. The monitor changes brightness levels in a sudden and fast way that can be very irritating and adds eye strain. But if the flicker gets too bad, there are some things you can do.
1. Set your monitor to its native resolution and refresh rate.
2. Ensure all video and power cables are properly connected on both ends.
3. Try a different video cable.
4. Test the display with another device, so if the flicker occurs when using your PC, try the monitor with a console, a different PC, Blu-ray player, and so on.
If the flickering persists, please contact BenQ Support.