It could be allergies, pain or anxiety.
My 4 year old spaniel has been licking her paws and showing other anxious behaviours, like excessive barking, whining if left away from me. My husband died in October, these behaviours followed bereavement, so I’m trying to help minimise opportunities for her to practice the behaviours. Rescues need 3 months to begin to settle. Lucky he found you.
Food could be a trigger, lots of dogs are allergic to chicken products. Tinned Chappie was recommended by our sensible vet for one of my rescues who had awful gastric problems. I use it now for any of my dogs with stomach bug that doesn’t need the vet.
Best of luck, my rescues have been grand dogs - much easier than my prima Donna of a pedigree lab 🐕