troubleshooting – Friends phone keeps rebooting & other problems

A friends phone keeps rebooting, & when it does it resets their theme to the default theme. A couple times it has gotten stuck on the bootscreen requiring a battery pull to fix it. Just now after opening google photos which they have been using for a long time without any problems a popup suddenly appeared asking for permissions to access photos & wouldn’t allow access with clicking allow. The phone is a Galaxy On5.