I had the same problem after 8 months of using the phone without a hitch.anybody facing "sudden death" issue ?
my fone has been lying on table since 3 days ... it boots after it gets fully discharge and plugging it to charger .... boots ... & becomes dead again, no response to any key or combination of keys (tried hard reset and force power off button under the sim flap)
if anybody has a solution then please share !
refer this
It's a motherboard issue.
I was able to revive it and do a repair with PC Companion, and after 20 days or so, it happened again. I sold it because it was not under the warranty any more.
I bought another Z3C, but now I think I made a mistake, because, judging from the sony forum thread, the sudden death is inevitable at some point.
The longer you have the phone, the greater the chances of sudden death.
Maybe it has something to do with the manufacturing date. Mine was from week 38, 2014.