White lines displaying and blinking on my mackbook pro mid 2012 13 inch

i have a mackbook pro mid 2012 13 inch. My macbook is show white blinking lines on the screen. sometimes after the apple logo appears before login screen comes out and sometimes after spending sometime on the laptop and then instantly no where the screen shows the blinking lines.I am attaching a photo so that you can see what I am talking about. I have recorded a video too. I can shared it too upon request. Please let me know what exactly the problem is.