Why my phone is hang

Shravan, you're going to have to give us more to go on than that if you want help. Exactly where does it hang? While it's booting? When you start an app? Is it a particular app?

What does it do when it "hangs"? Does the whole thing lock up, or does the app just stop responding? Are the touchscreen and buttons still working?

We have no idea what you mean, so the more information you can give us, the better your answers will be.