I had it a few months ago, it would come and go...almost rendering me immobile for about a minute. It gradually spread to my back too, and was quite worrying.
Apparently it can be brought on by stress or pulling a muscle. I was put on Naproxen for 5 days. To be honest, I'd take a trip to your gp after the holidays. Better safe than sorry, but most likely to be a strained muscle.