Good looking dog. Is that a Papillon? Hot girl I lived near for a few years had one of those, and like most women (scratch that, most people in general) she did a half-assed job of training it. It was super smart at some things, but then there would be obvious training failures like going absolute apeshit when someone came to the door, or she had to leave quickly without spending like 30 fucking minutes preparing the dog for her departure, etc. Hers always had that nervous chihuahua shake too, but maybe that's just a small dog thing.
Yes, its almost prescient that you mention this
our family got two Papillon females from the same litter (we were originally thinking about toy/mini poodles)
We spent 3 months very rigidly house breaking, she never makes a mistake now, and gets her business done outside in under 2 minutes. When it comes to training, this dog wants to listen, and she feels guilty when she thinks she's done wrong (even when she hasn't).
The other female is still not house broken about a year in, because the other family member did not regiment her training, and did not spend enough time at home with the puppy during her formative months. The dog, basically ignores people, and its a shame.
Growing up with a dog, that was insanely difficult to control, its frustrating to see a dog that could easily be excellent, have such poor behaviors. All dogs need committed training, and a stable household (my household growing up was a fucking nightmare), but this breed, and especially this particular puppy, took to it very easily. She wants to behave and listen. My Beagle was from a hunting liter, and had an enormous prey drive, and simply had difficulty redirecting her energy, or understanding commands.
As far as the barking, ours didn't and just started to now (we think other yappy dogs she's encountered have played a role in her territorial barking) so we are working on that now. The shaking is not uncommon depending on the "energy" of the room, e.g. MIL just lost her Papillion this Weekend, so we held a a little funeral, and everyone was sad. So our puppy who was at the funeral, started shaking and sat under a chair quietly until she was comforted. My guess is it was an encouraged trait in breeding, these are after all basically the original toy breed made for women to baby.