Q: Ipad air restarts automatically in screen-locked mode and sometimes restarts after blue screen.

Greetings Tixcat,

Welcome to the Apple Support Communities!

I understand that your iPad is restarting unexpectedly. To begin troubleshooting this situation and for more information on how to proceed, please read over the information in the attached article. 

If your iOS device restarts or displays the Apple logo unexpectedly - Apple Support

Cheers