IPhone 4 refuses to turn on

After playing a game on my iPhone 4 I locked it for a few minutes and when I tried to unlock it, it just gave me a black screen. I tried the hard reboot (holding the lock and home buttons) and saw the Apple logo, but it wouldn't go away after a few minutes so I've tried that reboot for what feels like a thousand times, but it won't turn on.

I tried connecting it to my computer and putting it into Recovery/DFU modes, still nothing

I think I've tried every possible method I could find, and the thing just absolutely refuses to start up. Is there still hope or should I just take it to the Apple Store?

There must be problem with motherboard of your iPhone get check it in service center. Another problem is of software it can get corrupted need to reinstall it. Best way go to service center