Does your unit power off at all when issue happens? No autoreboot?
Does your xperia overheat or there is a high battery consumption?
Does your phone power off by itself even in flight mode?
Does issue happen when unit is on stand-by?
How ofter does it happen?
Most likely this issue is caused by a app/process that isn't working correctly
Check if issue is the same starting the device in safe mode
- Turn off the device.
- Press and hold down the power key until the phone vibrates.
- Wait until the Xperia™ logotype disappears.
- Press and hold the volume down key. The device then restarts in safe mode.
- To exit safe mode, restart the device.
