iPhone Not Fully Loading to Home Screen

My iPhone won't startup. It shows the white screen with the black Apple logo for three minutes or so, then turns off. When I hit the power button, it tries to startup again, with the same white screen + black logo. Then two minutes later, turns off again. I tried holding the power + home buttons to restart, same result.

It just doesn't fully load. Nothing unordinary happened before this. It wasn't dropped or anything like that.

Any suggestions would be highly appreciated. Thanks in advance.

EDIT: I haven't had a chance to back up the phone in a while, so any solution that doesn't involve restoring from a backup would be highly appreciated.