iphone 6s plus wont start

I have an Iphone 6s plus and was using it last night, this morning the screen is blank and I don't seem to be able to turn it on. I plugged it into my laptop to see if I could open it in Itunes but it said the item attached via usb is overheating the hard drive!

I went onto apple.com to see what to do and it said I recommended sending it in, but when I put in the serial number it said I can't do it because I need to turn off find my phone! (how I do that when I can't turn it on beats me!)

I don't have another phone so can't even just ring up!

HELP!!