@Eric667: Do you see any notifications or error messages prior to the restarts? If you have installed any third party apps recently, please try uninstalling them to see if the issue is stemming from an external source. You can also try closing any background apps that aren't in use via the Recents button in your Navigation Bar, or head to Settings > Battery and device care > Optimise now (if prompted) > Memory > Clean now. You should also ensure that your device is up to date via Settings > Software update > Download and install, followed by Settings > Security and privacy > Updates > Security update.
