Whats happening?

On my free time a play alot of Clash of Clans witch is a game on the app store, When i leave to go and get a drink or help my mom or even when i am just sitting on the couch a message come's up and says "Anyone there" " Due to your inactivty we are resarting the app" or somthin like that. Is this just them game or the IPod, If its the IPod is there a way i can disable this.