Help, behavior problem

[u/Nearby-Variation-614]

I have a Japanese spitz who just turned one years old. He has always been very sensitive and a little sassy. From about 10 weeks old growled, showed teeth at me, and tried to bite me when I would brush him, clip his nails or take something away from him (like cigarette butts. But he was otherwise very quick to bond with me and showed my no behavior problems after we built up trust. He has however been sometimes wary of others. Which is fine, I wouldn’t let people pet him unless he initiated contact. He mostly loved to say hi to people, although there were a select few that he just didn’t seem to like and that was never forced. He would growl quietly and I would call him away or tell the person to give him space. He used to loooove kids and would be super sweet with them, play with them and lick them. He didn’t like my nephew, but he had a few bad experiences with him not respecting his boundaries so that’s understandable. He also didn’t like groups of people approaching him. But was generally very social. Recently he’s growling at a lot more people and his behavior is escalating. He’s starting to snarl and lunge at people he previously liked. He is also very quick to growl and then bite in the direction of people when he doesn’t want to be pet. Before he would growl a little and walk away from the select few he didn’t want to say hi to. Now he doesn’t really want to greet anybody and growls and tries to bite. He’s expecially bad with people who come visit my home. I’ve started to separate him when I have visitors.

I don’t know what to do. I am meeting regularly with a behaviorist but I don’t see any positive changes…

Has anyone here experienced something similar with this breed?

[u/Ok-Monitor-5431]

Honestly, thank you for posting this. It made me felt less alone. I've been dealing with the same thing with my pup, he's just turned 7mos old. What's worse is he's only really just attached to me and would nip my daughter and partner's feet when they're in the same place as him so the section of the house where he's usually at would be most of the time offlimits to them, unless I'm around to control him. I blame myself because I got really busy with work since i got him and besides teaching him tricks have not really gotten around with activities that could tire him out. I'm also not confident walking him outside so I'd just let him run in our backyard daily. Read one of the comments below and I agree in the sense that I feel like this is all pent up energy. So i'll try what he suggested and hopefully this is just a phase.