Your phone's motherboard is having defect so if your phone is under warranty period get it replaced at the nearest service center and if the warranty period is over then it will cost around 7 to 9k.
Well now the best option remains, to take it to a good service center.. How long have you been using it? It's can be battery failure... I had same issues with an Asus phone..
Many users reported about this issue here. For some users, it got fixed after factory reset. For some users, after Flashing new firmware. For some users it fixed after changing motherboard. For some users it was fixed after next software update. For some users, it is not fixed even after following the above tips. But noone knows the exact solution for this issue. Take backup of your important data before it's too late. You can't get your data back if your phone is dead.
In case the issue still occurs. Please register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).
