First, the wiring problem. First, check the line connecting the monitor and the graphics card. Then look at the power cord. If there is something wrong with the line, there is this phenomenon.
Second, the display hardware problem. It is recommended to take it to the dealer for testing.
Third, the graphics card problem. Generally, motherboards have identification function, which will give an alarm when the hardware connection is not good or the hardware does not match. It is recommended to reinsert the monitor into the video card.