What is causing a single hiccup at start of IOS game?

Once I launch the game and choose start from the menu the game runs fine until the 4th bullet is shoot(side scrolling shooter) or the 3rd or 4th collision(with my shooter and enemies but not the ground). At that point the game hiccups(freezes for 1sec). After this point the game runs perfectly and I can also reload the level with “Application.LoadLevel()” with no hiccups. To cause the hiccup again I need to exit the app and reopen it.

As my game is a side scroller I have enemies instantiated from the right(moving left) and the bullets are instantiated from the shooter(ship in my case) moving right. The ship can move in all directions but only shoot right.

Some notes

  • All enemies and ground have/has 2d box colliders
  • The bullet also has a collider, but also has a rigidbody
  • The shooter(ship) also has a collider and rigidbody
  • I do not have any objects instantiated at start()
  • This does not happen on android or in unity
  • I have tested iOS 8.1, iOS 7 including iPad, iPhone 5 and iPhone 4S all giving the same results.

Thank you for your help I will provide more information as needed and update if I myself find a solution. Thanks again.

In my experience, GameCenter, Facebook SDK, Google Analytics, Ad Mob,… (or other 3rd party library that use the internet) can be the reason.
You can run the game through Xcode and monitor what exactly causes the hiccup.