freez and autorestart every few minutes

[Mazahirabbas]

My device A51 still under warrany but start hang and auto restart every few minutes.can any one guide me.i already restore factory setting and software update but still problem same.can anyone guide me

[Om3r]

install software in boot mode by pressing power button and volune down together for some mins.
OR
Use KIES on pc and reinstall your software.