Will iPhone 4 turn on automatically when charging?
Solution 1:
Yes, it will turn on once it reaches the minimum charge needed to start the phone.
When the battery is completely drained, you would just see a depleted battery icon (with a connect to charger prompt) for a few seconds if you press the Sleep/Wake button or the Home button. Once you connect it to the charger, it will charge for a few minutes and automatically start up, taking you to the lock screen.
At any time, you can wake your phone by pressing either the Sleep/Wake button (on top) or the Home button (below the touchscreen).