I shut my phone off and turned my phone back on in my pocket and it automatically was in safe mode. I couldn't find apps I had installed and some of my widgets aren't working. What happened to my phone and how could I get it to be "normal" again?
In Xperia U you will get in to safe mode when you keep taping on menu button while the phone is booting.
Safe mode prevents any third-party apps from running. So if you have installed an app that might cause some serious problems with your device, boot it in safe mode to uninstall it.
You can boot into normal mode by a simple restart.