So, my macbook pro is shutting off at random times. Ill be in the middle of something mundane like an IM chat and poof its now off. Once it is off, it wont turn back on. When I press the power button, the white light at the front of the machine turns on then off again immediately. After a while it just magically boots. Sometimes after booting into the os and loading a few apps, poof off again. My battery is at full charge and my power cable has a green light on it. I have done a SMC reset, but when I try the prram reset it wont turn back on. I am at wits end. I will say I bought this thing used and it has no apple care. It is the i5 model if that matters. Thanks for any help.