If it went off due to battery empty please try the instructions below
- Remove the battery
- connect to charger without the battery
- Press and hold the power button for 15 sec while connected to charger
- Insert the battery
- Allow the phone to charge for 10 min
It should be able to charge at this stage.
If it went off but the battery was full that will be hardware problem for this case you must send it for service or check if the battery contact are not dirty (both the battery and the phone)