May be loose cable, it is recommended to send to the service center for testing
Or try the following method
1 .Pinch the upper left screen with your fingers. The center of the position is about the number of digits and the date of the minute (the position is important) [the position of the screen opposite the sim card slot], pinch and apply a little pressure, be careful not to crush the screen.
2 .Restart or turn on the screen, keep the screen pinch until the boot time and date are released.
