Sorry about that last sentence, it was meant to say "Does it turn on again immediately after turning off." I can only think of a couple of things to try off hand. You could try running the computer without the battery, DVD/CD drive, and any extra devices unattached and see if the problem resurfaces or goes away. If it does go away, you can then add each piece one at a time until you find out which piece causes the problem.
Of course if it doesn't go away, then some other troubleshooting would need to be done.
Hardware Support Specialist