My MBP cant be started after 4 months I havent use it

Hello my name is Kiki. Im from Indonesia. I have a question about my MBP. I haven't use my MBP for about 4,5 months and when I started it up last night the screen showed me grey screen and folder box with question mark. I really need your help because all my data there and Im about to finish my study. Is the hadisk safe? I mean can my MBP run normally? FYI, my Macbook type is MBP with 14" and I bought it on 2012 and OS Lion/Mountain Lion, RAM 8GB, hard disk capacity 750 GB, processor Intel i7. Please Help me :((((