White line down half of screen and partly unresponsive, randomly

So for a short while, a strange thing has been happening with my 7 month old iPhone 5s. Randomly, just when I open my phone there is one bright white line going half of the way down the screen from the top which fades as it goes down, and part of the screen is unresponsive. Most of the time, it's completely fine, which is why I asked this question rather than using the forum tips, as most people have this all the time, and I didn't know if it would be any different. It's fine, but it's kind of annoying sometimes.