iPhone 6 is not responding or turning on.

My iPhone 6 (64GB) is showing apple logo and empty battery logo when I plug the charger in but is not fully turning on or restarting.

I have the latest software update. similar situation happened in the morning but after a while it turned back on when I plugged in the charger. A guy in apple store told me to connect it to my mac and hold sleep and home button when connected to iTunes. This did no help as it is not responding at all.