(redirected) Alienware x51 R2 problem?

Hey guys! 

First time posting on these forums; apologies if i'm asking in the wrong place! 

I've had my Alienware x51 R2 for 7 months now; and I love it. Its the perfect size for the space I have, and it packs the right amount of punch for the games I play. 

However, two days ago, I came in after popping to the shops, and went to turn it on and it wouldn't. It would start up, the lights and fans would kick it, and it would do one beep, before shutting off and repeating that process. It did this endlessly until I unplugged it.

I left it unplugged for 2 days, and then went to try again this morning and it worked again! This is great news for me, but I would like to know what may have caused this, and whether there is a chance it may reoccur! 

Thanks in advance!