Could be that he has water in his ears from his bath.
Check inside the ear, if it smells funny or looks a bit waxy then give them a clean.
If the shaking carries on I would take him to the vet because he may have ear mites, Poppy had these when we first got her and she would constantly shake her head and scratch her ears.. but not all dogs react the same as my other dog caught them from her and didn't shake or scratch at all.
__________________  Rachael & Poppy |