Auto restart

A. Clear Wipe Cache Partition.
Steps to perform.
1) Turn off the device.
2) Press and hold the Volume Up key and the spower button.
3) When the Android logo displays, release all keys.
4) Press the Volume down key to navigate and select "Wipe cache partition".
5) Press Power key to select. When the wipe cache partition is complete, Select Reboot System.
6) Press the Power key to restart the device.

B. go to safemode and observe is there same issue in safemode too
if not then problem may due to other downloaded apps
and if same issue in safemode then try to visit service centre

steps to turn safemode;
long press on power button>
long press on power off option>click on safemode >your mobile will restart and turn into safemode.

Keep in mind that in this mode only inbuilt system app will work

Dear Samsung Member,

Greetings from Samsung Customer Support!

 

To resolve auto restart issue please follow below given steps:-
Go to Settings > General management > Reset > Turn off auto start.

 

If the issue still persist kindly visit the service center for the physical inspection of your device. To check for the nearest Samsung service center kindly click on the link:- https://www.samsung.com/in/support/service-center/

Thank you for writing to Samsung.

Warm Regards,
Samsung Customer Support