Can't leave or close apps
My iPhone 5 (iOS 9.1.2) has recently developed the annoying habit of not allowing me to leave apps. If I click on a notification whilst using an app the notification disappears, the home button does nothing, and if I lock my phone, the screen stays blank. The only way to get out of the app is by resetting the phone. This is becoming increasingly annoying as it happens several times a day. Any recommendations on how to solve this issue would be greatly appreciated.
iPhone 5, iOS 9.2.1