Sudden changes in behavior like this definitely warrants a trip to your veterinarian. Sometimes dogs having physical discomfort, systemic processes going on (liver, heart, kidneys, etc.) or neurological changes can suddenly lash out at their owners. It is best to have all physical possibilities ruled out before treating it as a behavior problem. If the doctor rules out any physical reasons, then a good behaviorist should be able to help you. A dog that is acting aggressively by snapping at you is dangerous, so please be careful.
Medical emergencies should been seen by a Veterinarian immediately.
If I've been helpful, please click the GREEN ACCEPT button in the right corner. For more information, please click REPLY.
Bonuses & feedback are greatly appreciated :)