Battery?

[Fp3]

My Sony Xperia z3 + currently likes to switch off randomly even when it's has charge, and it will refuse to switch back on- only when I plug my charger in does it begin to work again. I don't know what to do, whether to replace my battery or whatever? I need advice  

[Uliwooly]

@Fp3 

Before you send it in to get a new battery, connect the phone to a different wall charger > press and hold power for 10 seconds > let it charge for 2 hours > try again, see if that does it