I had a similar thing with my Nutmeg. She's about 9 months old now and every few weeks, something would happen and she would limp a bit. So, to make sure there wasn't a recurring injury, I took her in and the vet checked her out. Even though she was no longer limping when we got to the vet, the did xrays and the xrays were clear. However, the vet did say that as she is still a puppy, her joints are developing and it was good to check it out as the knee/elbow is a complex joint and could easily get misaligned. He also said that this can be common with a corgi as their front legs kind of turn out a bit. He said just to keep an eye on her and try to keep her from being too rambunctious when playing. To which I replied, "Right, she's a puppy" and the vet laughed. So, if you're really concerned about your dog, go in and have an xray done. They will need to sedate your dog for the xray and you will have to right the check. But, you are the only one who can decide if you'll get piece of mind from taking those steps. Good luck.
An occasional limp that goes away in a day or so isn't much to worry about. We all limp now and again, for various reasons that usually pass, or that come and go fairly harmlessly. But it might be a concern that this seems to have recurred. It COULD be something entirely different, in which case it probably will resolve in due time. But just in case, it might be worth asking another vet for a second opinion.
For something like this I would take Murray to his Vet/Chiropractor who is a different vet than I take him to for other things. She is better at finding and ultimately fixing such things. I started taking him to her to make sure he stays in shape for agility. Many of my agility friends take their dogs to her. If you want a second opinion that sort of vet might be good to consult with. People who participate in dog sports could steer you in the right direction.