If it is switching off again and again then you can format your phone from samsung care and problem still exists again then it may be a hardware problem like mother board failure. You really need samsung care service.
We acknowledge your query and apologize for the inconvenience caused to you and will surely assist you regarding the same and please follow the easy troubleshooting steps which might help to solve the issue.
There are two methods to disable the auto-restart function Method 1: From the home screen swipe up or down to access the App Screen > Setting > General Management > Reset > Auto Restart > To Turn OFF auto-restart slide the slider toward the left. Method 2: Go to 'Settings'>>Tap on 'Battery and device care'>> Tap on Three dots>>Tap on 'Automation'>>Disable 'Auto-restart at set times' if enabled
If you are facing this issue after installing any new application then uninstall that application. Navigate to the Apps screen and tap on Settings>>Tap on Apps>>Tap on the desired app>>Tap on Uninstall>>Tap on OK
Reset settings: From the home screen, click on Settings>>General Management>> click on reset and then reset setting.
In case the issue still occurs. Please register your concern in Samsung Members Application (Open Samsung Members Application > Support> Tap on error report > Type your query > Send).
Thank you for writing to us. Warm Regards, Samsung Customer Support.
