My cat does it when he's stressed. For him, stress = not getting tonnes and tonnes of love, but any upheaval or changes in your household could cause this.
I would rule out allergies with a vet and consider stress as a potential culprit.
Chase (Friendly Resident Wigglebum) - Border Collie/Lab/Shepherd X
Kailey (Misunderstood Gentle Beauty) - GSD & foster failure #1
Rupert (Gold-Medal Winner of the 3 a.m. Kitty Destruction Olympics
Heidi - RIP my sweet baby girl