iPhone 6 Won't Turn On AGAIN (second phone)

Hi guys,

So I've been a long time Samsung customer... finally decide to make the move over to Apple, and I couldn't be more disappointed with my decision at this point in time. I bought the brand new iPhone 6 a month ago and earlier this week it stopped turning on. Randomly, it started to turn itself off. I had to use the hard reset buttons to bring it back to life, only to see it turn itself off again 5-10 minutes later. Fed up, I took it to the Apple Genius Bar, where they told me this was a very rare problem (despite the fact that the lady next to me with an iphone 6 had the same exact issue and the guy who took her place afterwards ALSO had the same exact problem). I got a new iPhone from them... problem solved?

Now, this morning (mind you this is the same week in which I just got a new iPhone 6 and this is all within my first month of even owning an iPhone), I woke up to a 2 day old iPhone 6 that... surprise, surprise.... won't turn on again! This is absolutely ridiculous, I have to think the flagship iPhone 6 is the worst phone ever created?

I literally cannot think of a thing that I've done wrong, I'm extremely light use and plug my phone in every night just like every other human being. The last app I used last night was the March Madness Live app, but have seen no issues with it looking online (and it isn't like I left the app on + streaming all night long or anything). I really only use the most generic apps on it. I haven't even had a chance to load up music / etc onto my iPhone because it just constantly breaks on me.

Any ideas on what could possibly be wrong? I've tried all suggestions I've seen online, and this is literally my second brand new device to have the same issue. I'm basically using a $750 paperweight at this point. Any ideas are appreciated.