It looks like walking/raining noise, and it’s usually caused by not dithering. On a lot of setups you dither every few exposures by moving the scope a few pixels in a random direction, and when everything is realigned and stacked, it should remove the noise.

I’m not that familiar with smart telescopes, but see if it has a dither function built in. On more typical rigs you’d dither by moving a guide star over, and I think NINA can just blindly slew a mount a few arcseconds if there’s no guider attached.