Hi @賊魚, let me see if I can help out here!
I have translated your question to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you.
Has this behaviour been going on for a long time or has it just begun to happen? Also, does these restarts occur during a specific kind of use or do they happen randomly?
The first thing that I would like you to try is to run your phone in safe mode for a while to see if the restarts happen there as well. Safe mode is a troubleshooting mode where all apps downloaded from Play Store is temporarily deactivated, that way you can see if this behaviour is caused by a downloaded app. For more information on safe mode and how to use it, click here.
If the restarts occur in safe mode as well, my suggestion is to try to repair the software using a computer and Xperia Companion. Keep in mind though that a software repair will erase all user data from the phone, so make sure to do a backup of your user data before the repair.
Try these measures and let me know how it goes!
