xperia T won't turn on

[231299]

I have an issue with my Xperia T, it started when i took my sim out of the phone and inserted into another phone, then when i tried to put it back in my xperia T, my phone won't start up.  It looks like its starting up, it shows the sony logo and xperia, then you see the logo and it looks like its starting, then it hangs up and the phone retstarts and goes back to the sony logo again.  and this keeps going and going for hours without anything happening.

I have tried everything like restarting with holding the power on and the volume up and I have charged the phone fully, and i have tried connecting it to my pc, but oviously because the phone doesn't  start up properly, even the pc companion cannot read and connect to the phone.

[Hampus]

Hi and welcome to the community! Since you're new please be sure that you have checked out our Discussion guidelines.

Have you tried to power on the phone without SIM- and SD-card? If the same behaviour appear without SIM- and SD-card, I suggest that you perform a software repair via PC Companion:
http://support.sonymobile.com/global-en/tools/pc-companion/

In PC Companion you press start on Support Zone > Start on Update the phone/tablet software > Repair phone/tablet (the blue clickable link in the message) > Follow these steps without having your device connected to the PC.

Follow the instruction that appears in the program and do not connect your device until this guide tells you how to connect it.