Phone froze and is now not powering on (no-command error)

[rossandler]

I have a Samsung Galaxy Mega 6.3 I9205, I have owned it for nearly 2 years, i was on YouTube while it was plugged in and then the screen froze but the sound continued and none of the buttons were working so i took the battery out, put it back in and it won't turn on, I've tried rebooting in recovery mode and the screen comes on and shows me a robot lying down with 'No Command' underneath it but doesn't give me any options, after a few seconds it turns off and it tries rebooting showing me the Samsung logo and then it just doesn't load anything, Can anybody help?