Why iPhone 11 is restart

There are a few different problems that can fall under the category of auto restart, so it's important for us to know exactly what you mean. Sometimes the phone only gets as far as displaying the Apple logo, other times it can get as far as displaying the home screen, but the most common issue is that the phone boots completely, lets you log in and works normally for exactly three minutes, then it reboots.

The last one is what I'm addressing today. Three minutes is the interval at which the phone scans its sensors. If it finds a sensor it can't read, it performs an operation called a kernel panic, which consists of logging the error, then rebooting the phone in an attempt to recover from the error. That often works for software problems, but when there's a hardware problem, the reboot doesn't help. As a result, the phone reboots then three minutes later it checks its sensors, sees a problem and reboots the phone - which it will continue to do to infinity and beyond because despite how smart a phone appears to be, they're actually stupid and will never realize that rebooting the phone again isn't helping.

Anyway, the key takeaway here is that there is a record of why the phone rebooted that we can look at and figure out why it happened. That will tell us what sensor it's having problems with, and that sensor can be replaced, fixing the problem and stopping the reboots. This wiki page will show you how to locate the panic log and how to interpret it. I've been in this situation myself, and three minutes is long enough to access the logs and save the data needed.

iPhone Kernel Panics - iFixit

Once you've located the latest panic log, either cut and paste or screenshot the first page of it, then come back here and add that information to your question. If you cut and paste, you can just edit your question and tack that to the end. In the case of a screenshot, this guide will show you how to add an image to your question.

Adding images to an existing question - iFixit Repair Guide

Once you've provided the panic log information, we can help you determine what's gone wrong and how to fix it.