I have bought the phone in the middle of April 2020 from the authorized dealer in Latvia. From the beginning it was restarting. The first time was during the language selection on the first boot. I have tried to return the phone to the shop. They have sent it to an authorized Sony service. Service has found nothing, so the shop has refused to replace the phone or refund. I've contacted Latvian Sony support. They have asked to perform a lot of stuff - resets, software repairs, tests in the safe mode - nothing helped. They have asked to send the phone to the service again. I had managed to film the problem. I've send the phone to service with detailed description, with videos and with the claim. They have found nothing again. No one have seen my videos, I've never received an answer to my claim. But the phone continued to restart 3-4 times a day. I even didn't need to do something with it. I was just trying to unlock it with the finger print, but couldn't, because you have to enter a password after a restart.

Approximately in the middle of June Sony support have told me, that the are starting an "investigation" of my case. I was waiting nearly for a month for an answer. The answer was to update the phone with the latest firmware update. I was waiting for another month for this update to be available in my region. The update has changed nothing. Sony support is telling me to send the phone to the service again. As if it will not be the same as it was 2 times before.

At this point about 4 months have passed, since I reached Sony support and asked for help. At this point with no results. The phone is still restarting on random occasions. I hope to find some answers here.

https://youtu.be/Fs1MxO0-TLo - the video, no one from Sony support have seen.

Can anyone help me?

P.S. It is not a problem with the SIM card. I've started to use the phone without SIM card, while I was waiting for a nanoSIM from my operator.