Touchscreen Not Responding Randomly?

Hello

sometimes my iphone 6 plus 16GB touchscreen not responding to what i do. This happen randomly but recently i had another issue that when i touch the screen the thing i have touched have a rectangle appear with white border and i cant open my iphone ( Ex: when it said slide to unlock i move my finger on the screen nothing happen just the rectangle appear as you can see in the image below )? After i use my touch ID my iphone unlock and the issue have gone? So Whats The problem?