I do the Erase All Content and Settings, How can i restart my i phone 3s?

1. Reset the iPhone by holding the sleep/wake button at the top right of the device and the home button at the bottom center of the face at the same time.
2. Hold them both until you see the screen go black. In some cases, you may need to keep holding them even after the red power off slider appears. If it does, just keep holding it.
3. Wait until the white Apple logo appears.
4. When this happens, you can let go - the iPhone is rebooting.

An iPhone reset will not normally remove or delete any data or settings. However, the term reset is also sometimes used to mean deleting all content from the iPhone and/or restoring from a backup.