I had this issue too, put my phone to charge for the night and in the morning, very hot and won't turn on. Tried replacing the battery (with another genuine one), let it sit for a few days with battery out, nothing worked. I sent it back to Samsung they replaced the whole device. Apparently it happens because the USB connector for charging is subpart and gets corroded over time. Preliminary signs are: leave the phone to charge without any CPU intensive apps running, phone gets warm to very warm (in some cases has to stop charging because too warm and safety kicks in). This will eventually wear the charging curcuit out and result in a dead unit again. Seems to happend after about 9-12 months. It is happening again to the unit they replaced, I ordered a USB flex (the whole PCB at the bottom with the USB port on it) to replace it and see if this fixed the heating during charging situation. Good luck