Please follow the steps below.
1. Check if video and power cables are secured tightly. Try gently moving the cables at
the connector back and forth to check for faulty cable or pins in connector.
2. Try another video and power cable
3. Check for electrical interference around monitor. Fans, florescent lights, radios, etc.
4. Ensure that the graphics card is securely attached.
5. Optimize refresh rate (Hertz) in graphics card setting.