If you can hold the session longer than 10 seconds, try to reboot in recovery (Vol Up+Home+Power at the same time). When you get to the recovery menu, choose "Clear Cache" on the menu using the Vol Down button and press Power button to "enter" the selection. Once the cache is cleared, reboot the system using your power button.
If this does not solve your problem, you will have to do a factory reset. That process is described on the forums in multiple places. Please remember to backup your local data, which will get erased during the factory reset. However, your data on your external SD card (if you have one) will not be erased. Once the reset is done, you will get into a recovery mode, and your apps will be automatically reinstalled through Google Play. You will have to reconfigure some of them.
Hope this helps.