I am having this problem too! I Got my Pad on Monday and have been using it fine ever since; falling head over heels for it. Then all of a sudden it won't start and does this apple logo - off loop instead.
What started it was that the iPad seemed to have frozen so I force-quit it by holding the on/off switch. It would never start again.
When I turn it on I see the apple logo for a few seconds, then the screen darkens a bit showing the same logo for a few more seconds, then it goes completely black, then the whole thing starts over.
iTunes didn't recognize it so I tried putting it in recovery mode to restore it [http://support.apple.com/kb/HT1808] but that doesn't seem to have had ay effect
I am having this same problem. I have held down the top on off button and the main button for 30 seconds or so, until I finally got a connect to iTunes screen. But then I tried connecting to my computer and nothing happened. Eventually it returned to this loop.
1) batter charging
2) Apple Logo appears for start up
3) My passcode screen comes up for just about 1/10 of a second
4) Then it starts over
I have iOS 5 installed.
The problem started when I had the device plugged in, but it was not charging, and it went dead on me while I was playing a game on it. I think I have a trip to the Apple store in my future.