After owning my n800 for a year and a half, I think it's now failing. I normally leave it powered on all the time. On a plane trip a couple of days ago, I forgot to turn it off, and afterwards found it powered off. It was a short trip, so it shouldn't have drain the battery. I turned it on and plugged in the charger anyway. Then it seems to reboot itself every 10 seconds or so, sometimes even before a bootup completes. I then turned it off and charged it full while powered off. Even then, it would always powers itself off randomly, usually in less than 5 minutes of usage.

Do you think it's broken? It's now out of warranty. Is there anything could do to diagnose the problem and perhaps fix it?