iPhone 5 with genuine iOS 7.0.4 is rebooting, restarting frequently

I am sick of this iPhone 5 restarting so FREQUENTLY , it's become practically useless device to me. It's a complete disaster and wrong choice of phone.

This crash is happening since last week.

I am new user and I too have EXACT same problem on iphone 5 black version of the phone. It is running a latest authentic iOS 7.0.4 operating system and it's driving me nuts when call goes dead in the middle of conversation.

Also all the applications are closed and memory is freed up, still the same problem.