Once a while, are you shock to find out your Nokia Lumia phone screen display is enlarged by 4-500%. Or from the screen lock itself. You may taught Microsoft Windows Phone 8 is hang and need restart. You are right, restart is the immediate solution.
Somehow, this enlarged screen is a screen magnifier feature
1. Try double tapping the screen with two fingers whenever the screen is going to enlarge mode
2. Or the screen magnifier feature can be turned on and off in Settings -> Ease of Access
Official tips from Microsoft
Hope you find this handy..