Anyone knows how to read Iphone sysdiagnose ?

Hi, I have a very specific problem and I guess it has something to do with the IOS 11 itself! It has made my iPhone 6 useless! Was working find with IOS 10 and as soon I upgraded it started rebooting itself every 1 min I am chatting to apple care but I guess these guys just want to sell me a new iPhone!! I want to nail down the problem and tell them that its their ****** IOS 11! Anyone?