Well, that sounds like you're screen has a loose connector, i sugest you open up the phone, search through the guides to find the guide that is conform woth you're phones model, and that you fix this loose connection, the problem can acure when the phone has been dropped on the floor or that you dropped the phone to hard on a hard surface. Open up the phone, locate the screen connector on re-connect the connection properly, i hope this may help you. Greetings