Macbook Pro doesn't start up properly

I was on my macbook pro (which was very low on battery power) and once I was finished I put it to sleep by closing it, coincidently just moments before it was about to die. So I plugged it in, but when I returned to it some hours later, it wasn't responding when I clicked the mouse (I was confused because I hadn't shut it down but perhaps this was because it had died). When I clicked the power button it opened up directly to the sign in screen except it was all grey, distorted and momentarily frozen (the pinwheel was present for some time). After some moments it began working properly again. ANYWAYS the reason I'm so worried is because I literally just got the computer at most 3 weeks ago (I ordered it online from Apple). Should this be concerning me considering how new it is??