Hi my phone has recently started showing a triangle with tools in it when restarting and it's has now started turning its self off 📴 on its own it is an Xperia XZ1
I'd suggest that you perform a software repair using Xperia Companion. This will do a clean installation of the latest firmware and will also wipe your internal memory. Don't forget to backup using Xperia Companion, but preferably without adding apps or settings to the backup.
Follow the steps given in blue links, and keep us updated.
