Hi Neil. Welcome to justanswer.
This happens when the battery gets completely exhausted. Just connect it with the charger and leave it for 15 minutes. Then turn it on. Your phone will boot up. Nothing to worry. Reply for further assistance
Hi Neil, what is the status of the issue?
Try pressing and holding the power and volume down button for about 2 minutes and check.
Do you get anything on the screen?
Do you have a usb cable? If yes then try connecting your moto g to a computer for about 10-15 mintues.
If you don't have a usb cable then you can try a different charger
Is it under warranty?
If you are comfortable in opening it then I can provide you a link to a video.
It is a bit tricky and if you want to dissemble it then do it at your own risk. Or you can take it to a local repair shop and they will do it for you. Also this is not Motorola video. Just to give you an idea what actually you have to do after dissembling it.
CLICK HERE TO WATCH HOW TO DISSEMBLE IT
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Reply if you have any query.
Neil, so what are you going to do next? Did you try to dissemble it?
Maybe the battery has gone bad. The best thing is to get it replaced. Would you like to rate my services positively?
Neil, I will only get credited if you rate the chat positively. If you don't want to rate me positively then tell me and I will put your request for refund.