Ever since I've had my 16 month old Cavalier he has had these funny phases where he snorts loudly like a pig. Is he just trying to clear a bloked nostril / sinus? Is this normal? We do get funny looks if we're out walkies and he 'goes into one'.

Sounds as if his soft pallet is partly closing his throat. Get the vet to check, but I don't think it is possible to do anything. Ja:)kie

Do you think it could be dangerous - i.e. could he stop breathing?

No, he'll just snort, and drive you up the wall. Have it checked, but don't worry. Ja:)kie

it does sound like a soft palate , i own lhasa,s which are noted for doing this, when you first hear this it is quite worrying, but dont, all you need to do when your dog has a episode is hold his head put your fingers over his nostrils to block them and hold his mouth shut only for a second,and this normally does the trick, as he swallows when you let go of him this will unstick his palate,i find it normally happens when the dogs are dry and need a drink, as they always seem to have a good drink afterwards,there is no point you going to the vet and wasting your money ,like i did when first experienced this, there is nothing they can do, but if you are still a little concerned go to your vet even if it is just for your peace of mind, but dont worry he wont stop breathing