Do you mean the screen is blinking on and off? If restarting it didn't help, try starting up in "Safe Mode" and see if it flashes in there. If it doesn't, then you have something on the tablet (bad app, virus, malware, etc.) that is interfering and you need to remove it. If, however, it happens in "Safe Mode" too, then you need to have the tablet looked at for hardware issues. Either the connection to the display or the display itself may be going bad.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.