by Hard Reset
The Z250i phone turns itself off
Restart the phone or do a master reset.
To restart the Sony Ericsson Z250 phone
1. Turn the phone off and remove the battery cover.
2. Remove the battery and put it back in place.
3. Replace the battery cover and turn the phone on.
To perform a Sony Ericsson Z250 master reset
1. From standby select Menu > Settings > General > Master reset.
2. Select Reset settings to delete your changes to settings or Reset all to delete your changes to settings. all contacts, messages, personal data, and content you have downloaded, received or edited.
3. Select Continue.
If nothing works: As last resort do a Sony Ericsson phone repaire with PC Suite. Use this method to hard reset AFTER INSTALLATION----> TOOLS > PHONE REPAIR
Before you buy a new cell phone or new tablet, please try the following procedure to repair your device. First charge your battery, backup your important data if possible and in most cases take out SIM and SD card before factory reset. It is impossible to recover your data after doing a hard reset, so online backup is always important. For all of your data, a backup should be done on an external device, hard drive, raid system or media. With or without insurance, if your cell phone lost, damaged or stolen at least your invaluable data is backed up in a safe place. If you are about to sell your phone and you want to wipe your personal data, or if your phone affected with virus you have to do a hard reset. In some cases, you can delete the forgotten password or lock pattern from your device as well. All information is for devices with stock based ROMs. If you are using rooted device, always back up your EFS folder first, containing your IMEI info, etc.!