E3 restarting

[as169m]

Phone keeps on restarting until battery is fully drained

[Uliwooly]

@as169m

does it happen without the SIM card? 

[as169m]

Yes 😞

[Uliwooly]

@as169m

I'm sorry to hear that, you could repair it with XC if you haven't already, but you might have to stop by your Local support

Xperia Companion (XC)

Software Repair Guide

Alternatives on How to backup Xperias

http://talk.sonymobile.com/thread/36355

[Emir1]

Could you try to see if the same occurs without an SD card inserted as well? If it still happens after a software repair using Xperia Companion, without any SIM or SD cards inserted then I can only refer to @uliwooly advice to have it sent to an authorized service center. Contact your Local support for assistance in doing so.