ioS game app stutters upon activating

Dear developers, I am hoping you can help me out with a small issue I am having with IOs.

I am developing a game for android and ios tablets.  For ios ONLY, when it activates after being asleep (for both IPAD 4 and IPAD mini), the gameplay stutters somewhat.  It is almost as if it is running at a slightly lower frame rate.  I never change the frame rate at any point of the game (always set at 30).

Both the IPAD 4 and IPAD mini are brand new and do not have any other apps running on them besides those that are preloaded.

If I move back and forth between level screens and or the front title page screen of the game, and then go back to play a particular level, the stutter is completely gone and it plays normally. 

If I exit the game entirely and then restart the game, there is no stutter present.

Thank you for your assistance,

Justin