It is not uncommon for a smartphone to turn on by itself, and there can be several reasons for this. Here are some possible causes:

1. Hardware issue: The most common cause of a phone turning on by itself is a hardware issue. This could be due to a malfunctioning power button, a loose battery connection, or a faulty charging port. If the phone is still under warranty, it is best to contact the manufacturer or a authorized service center for repair.
2. Background apps: Sometimes, the phone may turn on by itself due to an app running in the background that requires a constant internet connection or access to the phone’s sensors. This can drain the battery and cause the phone to turn on even if it was previously turned off. To fix this issue, it is recommended to close all unnecessary apps and restrict their background activity.
3. Automatic updates: Many phones are set to automatically download and install updates when they are available. If an update is available and the phone is turned off, it may turn on by itself to complete the update process. To prevent this, you can disable automatic updates or set them to only happen when the phone is connected to Wi-Fi.
4. Smart wake: Some phones have a feature called “smart wake” or “smart lock” that allows the phone to turn on when certain conditions are met, such as when it is picked up or when it is in a trusted location. This feature can be convenient, but it can also cause the phone to turn on by itself if the conditions are frequently met. To disable this feature, go to the phone’s settings and look for the option to turn off smart wake or smart lock.
5. Ghost touch: A phenomenon known as “ghost touch” can cause the phone to turn on by itself. This occurs when the phone’s touchscreen registers touches that are not actually being made, and it can be caused by a damaged screen or a malfunctioning touchscreen controller. If the phone is experiencing ghost touch, it may be necessary to replace the screen or have the phone repaired.

In conclusion, there are several reasons why a phone may turn on by itself, including hardware issues, background apps, automatic updates, smart wake, and ghost touch. If the issue persists and cannot be fixed by the methods mentioned above, it is best to contact the manufacturer or a authorized service center for further assistance.