Help Xperia Z device won't boot

[Mutak94]

Hello,
I'm having a problem with my Sony Xperia Z. It recently overheated and automatically turned off.
When I try to turn it on I get past the loading screen and then a message "Optimizing application 1 of 243" appears, but the phone turns off again before anything is optimized. I tried turning the phone on while also pressing the volume down button, but then the loading just gets to "Optimizing application 20" (20-ish) and then just crashes again.
What can I do to fix this?

 

[Slug]

Install Xperia Companion on a PC/Mac, connect the phone via USB and try using the Software Repair option.