Today while I was at work my iPhone 5 randomly popped up with this screen;
The phone hasn't been reset or formatted since last week when I set it up and I had been using it all morning with no issue.
I clicked the back arrow at the top left and the phone went back to my homescreen and it is working fine now. But I want to know if I should be concerned about this?

The phone hasn't been reset or formatted since last week when I set it up and I had been using it all morning with no issue.
I clicked the back arrow at the top left and the phone went back to my homescreen and it is working fine now. But I want to know if I should be concerned about this?