iPhone 5 keeps malfunctioning- black bars

Yesterday, I went to use facebook on my iPhone 5 (ios 7) and the screen just faded to black and grey bars appeared, and it then just turned off and turned on. I thought nothing of it until today- I went to use facebook again, (not for the first time since the first malfunction) and my phone did it again. However, it is continuing to do it over and over: it will turn off, attempt to turn back on, and the screen will then fade to black and with screen errors (random red and green sections of the screen, the bars etc).

It has been doing this for the past half hour, does anyone who has had this issue before know any ways on how to correct it? I really don't want to have to go to apple to have it replaced, I'm fed up with all this.