Samsung — Series M freezing out and rebooting again and again(like 15-20 times in an hour)

Address:

South korea

Nisha Kumari this side, I bought samsung m21 in Nov 2020 and phone was working completely fine, Now sir suddenly in Feb, 2021 my phone have started getting reboot again and again, I have tried all and it is not getting sort out and it is suggested to change its motherboard, which costs around 5k-6k, please help me out of this, I bought this phone with the hope to assist my studies atheist for 2-3 years but it is getting unusable just after 1 year
Hope you understand, and look into this matter.