Is Jack the kind of dog who protects his territory? Does he growl at you or try to nip at you when you try to pick him up or get too close to his "spot" in your house? It is quite normal for dogs to be territorial, it is how they survive out in the wild. But in your home, this type of behavior should not be encouraged or accepted. In a domesticated situation, there can be many reasons why he feels the need to be territorial, such as having been teased or having his "things" constantly taken from him. But, with time, effort, and patience, you can help him get over his issues and make grooming a much more enjoyable experience.
Contrary to what many people think, dogs have excellent memories. They also have personalities that are as varied as the families who choose to add a dog to their "pack". If at any time Jack was mistreated or teased excessively, these would be good reasons for him to develop territorial behavior. But, long before you reach for a sedative or a muzzle, try these tricks to help you with your grooming tasks.
Training a territorial dog like Jack to accept being groomed can be challenging. But, as long as you are willing to put in the time and effort, the time will come when he actually looks forward to his weekly bonding sessions with you. Don't hesitate, just get out there make grooming a fun experience for both of you.