iPhone 5s restarting and flashing blue screen

Hi! Two days ago, my iPhone 5s started restarting (the way it will when you hold the home button and lock button at the same time) and flashing this blue screen at me, which I later found was the "blue screen of death". I panicked and took it to my Telus store, because I have warranty on it. The guy told me he'd never seen anything like it; usually he can buy enough time to actually unlock the phone and get into it, but my phone kept restarting and flashing the blue screen before you could even get into it's settings. He gave me a number to call, and Telus (or Apple, I'm not entirely sure) is supposed to be sending me a new phone. However, tonight it turned itself back on (I had turned it off because all it was doing was restarting and causing a big fuss), and it hasn't restarted or anything since. I looked at my camera roll, and there's a few weird pictures; I had similar ones enter iPhoto on my computer after accidentally importing my hard drive into the app. It's unclear how they turned up there, and I find the phone fairly slow after being turned back on. Now that I'm left with a phone that isn't very obviously broken as it was before, I'm unsure what I should do. I was instructed to send the broken phone back to the company, but I don't know if I should restore it now so none of my information is on it. Is this phone still technically broken, and should I just send it back as is?! Also, any solutions to the restarting problem? Thanks a lot! 🙂