You could start by going to i and logging in to check that your contacts are all listed correctly.Potential solutions: A bug that seems to have cropped up for a lot of people, particularly on the i Pad, but also various i Phone models is a random crash from the home screen which soft reboots the device and brings up a screen with the Apple logo.

You may find that they randomly return after a few minutes or a couple of hours.i OS 8 released for i Phone 4S, i Phone 5, 5S, 5C, i Phone 6, 6 Plus, i Pad Air, 4, 3, 2 and i Pod Touch 5 Gen. If you find download links like i OS 8 ipsw for i Phone 4, you must know - it's scam or virus, because Apple unsupported i Phone 4 in i OS 8.