My galaxy m31 is automatically restarting while using.

[Aswin_cr7]

My galaxy m31 is automatically restarting while using.what's the solution There is an update in the software (august). Will the software crash if i update it?? 

[Zenhal]

Go to service center and change motherboard

[PriyankaTank]

I have updated it, and plus I did factory reset and now my phone is not restarting
Earlier it used to once in a week even that is stopped
My phone was almost about to full its storage was more than 80% used, it slowed my phone also but now its good