Phone wont stop locking

[cillasan]

My Xperia Z3 started locking on its own, when I unlock it after 5 seconds or so it will lock again. I tried restarting it but it 'didn't help, it wont connect to the PC companion either so I cant run any updates. It still charges but wont connect to anything, I cant even access the settings because it locks as soon as I try to access it. 

[_alexdon_]

You may need to perform a software repair using PC Companion.The process will erase all internal memory.You might need to charge your device for about 1-2 hours before so the device has at least 60% battery.

Make sure the device is not connected to computer or laptop and turned off (sometimes you have to press power button and volume up until the device vibrates 3 times or on some devices you have to press the small button near the SIM tray or on the back of the device).

Open PC companion->support zone->phone/tablet software update->repair my phone/tablet blue highlighted.Follow the steps given,do not connect your phone until prompted to press volume down while plugging USB cable. If PC companion does not start the repair process, you might need to run it in compatibility mode with Windows 7 (in some cases XP).

[Uliwooly]

Try to boot on safe mode 

http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008#U348008

[Uliwooly · Accepted solution]

If neither PCC nor Safe mode work there's one more option

either MyXperia or Android device manager > on your computer access either one of them > and once it locate your phone you can perform a factory reset

keep in mind that for either one of them to work 

the data or wifi has to be on

gps on

you must know your gmail password

Android Device Manager

www.google.com/android/devicemanager

MyXperia

www.myxperia.sonymobile.com

[cillasan]

I tried to use the PC companion but I hadn't  used it before so when I select support zone it tells "this application could not be installed. Please try again later"

[_alexdon_]

Try what uli suggested.