Nexus S bootloops after trying to apply OTA update I have a Samsung Nexus S which I bought off my friend. A system update popped up and I hit accept without even thinking about it but the phone said I had to charge it so I did and left it for an hour or two. When I came back and went to turn it on it just went midway through the reboot and turned off again, then without even touching it it would repeat this process over and over. I have absolutely no clue what to do - how can I get it booting again?
I'd suggest you start here:


GUIDE Factory Images (JB-ICS-GB) (XDA developers)



  Requirements:
  
  -Android SDK
  -Java JDK
  
  -Platform-Tools
  
  -Unlocked bootloader ("fastboot oem unlock" pay attention, wipes everything, also SD card)
  
  -experience with adb and fastboot
  
  NOTICE: If you never used the sdk, the jdk, fastboot and adb, before installing the factory image YOU HAVE TO FOLLOW this guide in order to get sdk and unlock bootloader.


The part that is relevant to you, assuming your device wasn't running a rooted custom ROM before, is 4B:


  If you are coming from another stock rom (official older OTA unrooted), this doen't wipe your data/cache:


adb reboot bootloader
fastboot flash bootloader bootloader-crespo-********.img
fastboot reboot-bootloader
fastboot flash radio radio-crespo-********.img
fastboot reboot-bootloader
fastboot update image-********.zip



  if you want relock the bootloader (not necessary, only for warranty)
  do also these two step:


fastboot reboot-bootloader
fastboot oem lock 


Tried to include as much as possible for posterity, but the files you need and so on are in the forum thread anyway so this doesn't really apply if the forum thread would go down.

If you have any questions, please comment and I'll update my answer.