Why phone automatically off?

There are multiple potential causes depending on the specific details of your issue. You can try updating your phone's operating system just in case it's a software issue. If that doesn't resolve the problem, make sure your phone isn't overheating. If it seems like your phone is turning off because the battery drains unusually quickly, you can try turning off software that's running in the background or disabling unused services such as GPS or Bluetooth. If the quick battery drain continues, your phone's battery may have degraded over time and may need a replacement.