Dog immobile then having trouble walking.

Just now, my mother went to let the dogs back inside after they had been playing in the yard and found our cocker spaniel laying on our porch laying on his side and not moving. After a very short while he got up, but his torso seemed stiff/hard and he was having trouble controlling his back legs. He kept trying to run back and forth between us so we could pet him as per normal, and now he seems perfectly fine.

Something similar to this happened a few months ago. It was late at night and I found him laying on his back on the couch whimpering and unable to move. After some time he managed to roll himself off the couch and was having trouble controlling his back legs again, but after walking returned to normal.

It's only happened these two times, but should we take him to the vet? We haven't yet seeing as after the episodes he is absolutely normal.

[peekawho]

Yes, he needs to be seen by a vet.