This isn't really border collie specific I'm sure, but I have noticed some strange behavior as my dog has gotten older. I wonder if I should be doing anything... She does a strange circular nuzzling thing with her head around her food bowl before and during eating - so much so that the bowl hits the side of the wall and she practically turns it over. She seems to like to scrape her nose against the placemat several times before eating as well. The other odd behavior is she goes outside several times a night and just lies on the deck, often barking at nothing. She has a dog door in my bedroom so it wakes me up frequently. I thought maybe it was the hot weather but she is doing it on cooler nights too. She's 13 so some eccentricity is in order, but she's in great health so if there's anything I can do for her mind, I will do it!
I would try a food bowl that can't slide around, such as one in a raised frame, and then I would add a small amount of canned food to her dry kibble, if that's what you are feeding. She will be able to smell it right away.I have a cat who does exactly the same thing!
At her age, she may also be starting to experience dementia. Not uncommon in older dogs. As long as your vet says she's physically healthy, I don't think there's much to be done if this is the issue except enjoy what time she has left (which could be a lot) and forgive her her eccentricities. Try googling "dog dementia" and see if her behaviors fit the symptoms.