Xperia T, restarts/turns off when not in aeroplane mode or not plugged in?

[7Wang]

As the title says, my phone only works when in Aeroplane mode when not charging, if i take it out after about 1 minute it will constantly restart itself until i put it back into aeroplane mode or plug it in. I can only not be in aeroplane mode if im charging. This problem has been happening for awhile but it has recently got a lot worse, it used to restart once everyother day but now I physically cant use my phone safely which is a large inconvenience obviously. Please help, any help is greatly appreciated, I have a feeling it might be a battery issue but im not sure.

[_alexdon_]

Can you check how it is if you remove the SIM card?

[7Wang]

Hmm, seems to be good so far, will i just need to replace the SIM then?

[Thommo]

Yes you will but if it continues with a new SIM then your SIM reader or slot needs to be looked at as a faulty connection will force a power off

[7Wang]

But what does the connection have to do with it be plugged in, how come it doesnt power off then?

[7Wang]

I opened snapchat, camera based app, my phone just restarted (no sim) does this change the conclusion?

[Thommo]

All you can do is perform a system repair which will rule out software issues but if after doing so and using stock only it happens again then it could be a SIM issue or a hardware issue but if all is fine then you start installing 3rd party apps and it starts to happen again then this will conclude that the issue is an app