A Problem with Nokia 5530 Xpress Music

First of all, hi guys this is my first post.
Second, i have this phone for about 3 years now and i'm very happy with it, but today something happened.I get out of my bed decided to get a call to one of my friends and my phone automatically shutdown, i restarted it tried it again like 5/6 times still the same thing.The situation don't change when someone is calling me either...I have no idea what happened, this is just out of nowhere... :>
Any ideas ?
Thanks in advance, and sorry if my English is bad, it's not my native one.