As we know that computers hang / freezes up often, N8 being a multimedia computer, can also cause this hang / freeze problem though there are so rare chances for that (1 in a million). So we should be knowing what to do, incase this happens and phone doesn’t respond to any operation, as Nokia N8’s battery cannot be removed unless you remove its screws from the back of Nokia N8.
Now coming towards the tip:
If the phone freezes, the power button is doing the job just like the restart button on your computer, all you have to do is to press & hold on the phone power button for 8 seconds and it will vibrate 3 times then it will restart.
Note that it’s very hard to reach this point to make the phone hang/freeze but in-case it happened that what you have to do, And if it did not work * which is really hard * you have to visit the nearest care center to solve this issue for you.