My I pod 5g screen quit responding to touch a few times

I was playing Smule piano and the screen froze during game play. I was able to use the home button to get out of the game but the screen wouldn't scroll. I was able to use the on/off button to make it go to the lock screen where it would unlock but after a few moments the screen quit responding again. This happend 2 more times. I finally cut it off and so far it hasn't froze again. I was wondering why it froze and if I could do anything to prevent it from happening.