Either there is something fishy on the device, bad app, virus, malware, etc., or the display is going to need to be looked at by a tech (or the manufacturer if under warranty). Try starting up the tablet in "Safe Mode" (instructions below) and see if shows fine in there. If you can see on the display in there, then the problem is something on the device. You will need to then find and remove the cause and then restart (turn it off and back on) the tablet. If, however, it still does the same thing even in "Safe Mode", then you will need likely need to be looked at.