Reset,Reboot,Restore Your Iphone

Trouble Shoot Your Iphone:

How To Reset Your Iphone

The Iphone Has A Better understanding Of The Software And hardware But Sometime Some Apps can Cause Harm to your Phone.Since Your Phone Conatins All Important Contacts,Apps There Might Be Some Problem That Can Cause Your Phone To just reboot and becomes fine.
But even if the occurances are rare, there might be times when apps start crashing, and the device seems slower than usual.

If you not want to lose all the data be sure to create the backup of it the methods of creating backup are here:

http://digitalinspiring.blogspot.in/2013/06/how-to-backup-conatcts-message-app-for.html

Restarting the phone is likely to solve some issues. To do this, press the Power button for a few seconds and then use the slide-to-power off option on the screen.

Problem:

If the problem persists, you can try resetting the device back to its factory settings.
 To do this, go to Settings > General > Reset.

In Reset, you are provided with several options...
If the issue you are facing is minor in nature, like a laggy phone, for instance, reset your handset using Reset All Settings. Don't worry. This option will not delete your data or the apps you have installed.

If your problem is a little more serious, where your phone restarts by itself or freezes during use, try Erase All Content and Settings.
 If your phone has frozen, you can try a hard reboot:

Hard Reboot: 

Press the Power button and Home button simultaneously. Keep both pressed for around 10 to 15 seconds. Release the buttons when you see the Apple logo on the screen. Your phone will reboot.

 

If your iPhone isn't booting up, hard reset it through iTunes (data will be lost).
Reset Trough Itunes:
Open iTunes on your PC or Mac and make sure it is updated.
 Then, connect the phone to your computer. If the phone is switched on, iTunes will recognize it. If it doesn't , keep the power and home button pressed. iTunes will then detect the device in recovery mode. Follow the onscreen instructions on your PC to complete the reset and restore process.
http://support.apple.com/kb/ht1414