Replacement iPhone 5c bugs, freezing and malfunctioning touchscreen

So a couple of days ago my 8 month old iphone 5c went black and itunes restore or update stopped working. I took it to the genius bar and they said the logic board had conked off so they offered to replace the phone since it was under warranty. In about 45 minutes I got a new phone (5c) and as I was setting it up I noticed the device randomly froze 'in different parts of the screen'....

Let me summarize what I mean by this - I was going through the usual setting up process and suddenly the setting up process froze so that the 'next' button wouldn't respond. I immediately pointed it out to the genius representative. He switched off the device and restarted it and it seemed to be back to normal. However after gaps of say an hour or so it continued to display this behavior - the home screen went haywire - I would click on my amazon app and nothing would happen, I would click the home button and whatsapp opened and basically the phone looked unstable. I did a restore (not DFU) and it was fine for a little while but then again it froze on another app and all the buttons were doing something different from what they were supposed to - I would press the home button and it would go into contacts and so on.

This is a new phone barely 15 hours old and Im wondering what to do. Will a DFU restore fix this...or is it likely to be a hardware issue. The occurrences are random so I dont know if I should take it to Genius yet. Plus I just got this as a replacement. Will they replace this phone again?

Thoughts appreciated!