MacBook restarts instead of shutting down

I just got a new Macbook Air 13 inch a week ago, and last night when I went to shut it down for the night (by clicking on the apple logo in the upper right and then clicking shutdown) 3 times in a row it restarted instead. It since stopped doing this, but it worries me that this happened at all. I got this computer because I thought it would last me several years without problems, and spent too much money on it to be having problems this early on. Is there some setting I'm not aware of, or should I bring the computer back? I had just taken out a flashdrive and installed flash earlier in the day, but I don't see how this would have any effect.