Sudden reboot loop error

Suddenly my phone went to a restart , I was merely playing songs with AUX in speakers, I thought its a general issue but the problem is , it gets on whenever I put the battery I don't have to even press the power button , so after I put the battery it's on and as soon as the samsung logo comes it gets off again and thus the process is continuous , I changed battery , no use , I tried to get the boot menu but before I can do anything it's off , one repairman is saying that I have to change the motherboard , PLEASE HELP ME