What to do about random reboots or restarts after Gingerbread update?
I'm sorry you're experiencing issues after the update. If you've already tried pulling the battery then you may have to perform a factory data reset. This is necessary some times when experiencing issues after an update.
Note: When resetting your phone it will erase everything not stored/saved on your SD card. However there are very helpful applications on the market like SMS Backup & Restore that will back up your text messages. To back up your contacts you can go to Contacts/People application > Menu > Import/Export > Export to SD Card > Select Phone. Your pictures/videos will automatically be backed up to your SD Card. For backing up your applications you can use applications like Astro Filemanager.
From Home screen.
Press Menu, then tap Settings.
In Settings, flick Up and tap Privacy.
Tap Factory Data Reset.
You will see This will erase all data from your phone's your phone's internal storage, including Your Google account, System and application data and settings, Downloaded applications To also clear music, pictures, and other user, the SD card needs to be erased.
After this you will see an option for phone reset, click this.
Then you will see another option for Erase everything, click this.