IPhone Shutting Down Problem?

So, when class started, I turned off my phone, then a minute later, I checked my iPhone again, and it was on… So in lunch time, I turned off my phone ONCE again. It shut off for a few seconds, then coming back up again with the Apple sign. It didn't even shut down at all. And it's also making me lose my battery pretty quickly… Sorry, my grammars bad.

Save a back up of your phone on iTunes and restore it to original factory settings and then restore your update again, Sometimes glitches and bugs appear in the operating system, you just need a fresh start again.