Q: Macbook pro shuts off after loading halfway

I just recently bought my macbook pro, about 3 days ago. After I set it up, I turned it off and haven't had the chance to use it until today. At first turning it on it would show the load bar full but just stays like that. Now it will load about halfway before shutting off on it's own. If someone can please help me out it would be greatly appreciated. Thank you!