Xperia Z failing to turn on.

[fredc]

Left my phone in a car, found it very hot., after it was cool switched it on the SONY logo appears on my screen ,and then the phone just goes off. 

[JakeSully]

try doing a re-install if you don't have important data on it by using Sony Update Service hopefully that will fix phone death if not then overheating could of caused damage to your cpu, motherboard in the phone due to you leaving phone in the car so it got hot.