Xperia Z Unstable

[Expulse]

My Xperia Z, since I got it, has one major problem. It restart every 1-2 minute of using it and when plugging it, everytime.

What I tryied:

- Installing older firmware

- Updated firmware

- Changed battery

- Opened it and made sure everything was connected well

- Switched "Power Saving", "Wi-Fi", "Mobile Bravia..", and other settings in the Developer tab as well ON/OFF

- Flashed different firmwares on it

I don't know what is wrong with this phone. I can't get another one either because I didn't buy It..

I also want to say I have no Sony Service I can send it to, I'm nowhere near one.

[FrontierGate]

Which country?  Maybe a neighbouring country has an authorized Sony repair centre?

[Expulse]

Romania but I won't go to another country just to fix an old Xperia Z. I want someone to maybe tell me how could I fix it.

[Uliwooly]

@Expulse

Does it restart without the SD and SIM cards? if it does, it might be a hardware issue, what exactly its acting up, no one can tell unless you get it inspected by a Sony repair center. 

[Expulse]

It has no SD Card or SIM card and never had.

[Uliwooly]

@Expulse

Then the only option is to get it repaired by a Sony repair center, sorry.