Odd display problem in iPhone 6

I don't know if this is iOS 8 related or not but only got the phone three days ago so the top half of the screen sometimes will shift itself down to the bottom half of the screen vertically and leaving the top half blackened area not clickable/responsive. The display usually moves itself up back in few seconds but it is getting quite annoying right now.

I don't know how to post pictures from the phone to here as I've took a few screen captures.

Thank you for the tips!!! Hopefully I'm thinking too much and that's exactly what happen