iphone screen not responding

I got my phone at Christmas time and about last month my phones started to freeze at random times. when I say freeze I only mean the screen isn't responding so if I'm watching a video it'll keep playing, I just won't be able to pause it or anything. Some days it'll only freeze for like 5 minutes at a time but for the past two days its been completely frozen and I'm not sure how to fix it. I was just wondering if anyone else has had this problem.