Phone turns off when not on power when screen is unlocked

[colcook]

So this may sound straight forward but its a very random problem, basically my phone slowly started turning off(no shutdown just straight off) after long periods in the car using the SatNav even when it still had over 40% power on the battery.

Eventually the other day it just started turning off every time I tried to open maps (whilst lost in some random suburb!)

And now if the phone is plugged on charge I can do whatever I want with it, as soon as I take it off charge it will stay on until I unlock the screen and try to do anything (swipe or open an app.) Immediately I though the battery was to blame but why would it stay on until I did something?

Now the stranger part, if I start my music, start the satnav etc whilst its plugged in then unplug it, as long as I don't unlock or do anything on the screen the phone will continue to work. I can even start and stop music, skip tracks from the lock screen, even unlock and lock it again, as soon as I try to load an app, boom it just goes black, not even a shut down, just straight to black.

Anybody have any ideas? I haven't got it wet or dropped it, the only thing I can think is that maybe it was plugged into a dodgy charger and is holding some static but before I tear it apart I wanted to see if anyone had any ideas? I have booted into safe mode and the same thing happens?

TIA

 

[Rukbat]

the only thing I can think is that maybe it was plugged into a dodgy charger and is holding some static

That doesn't even not make sense. Touching a metal part of the phone to anything grounded (like a water faucet) would drain off any static, but chargers don't generate static.

but before I tear it apart I wanted to see if anyone had any ideas?

Assuming everything important is backed up, reflash the ROM.