Hi, i've had my macbook for about 6-7 months now which i bought from a friend. It's been working flawlessly up until about a month or two ago.. I've been getting random shut downs without warning from it. When i try to turn it back on it shuts back down. After about 3-4 trys of this ridiculous game it boots. Usually working throughout the day, but occasionally it shuts off again during my web browsing just 10-15 minutes after i turned it on. Any suggestions? Thanks in advance.