Iphone 4s stuck in recovery mode but progress bar doesn't move

My Iphone 4s used to just randomly shut down but I can usually restart it right away by just pressing the power button or doing the power + home reset.

However, on Sunday, 1/2 way into a phone call, it just died and can't restart anymore. I plugged it into computer and itune can detect the phone.

I try to do the recovery but it got stuck at "waiting for iphone" for a very long time and the progress bar on the phone stays in zero.

Any idea on whats wrong with it and how can it get it back.

Thanks