Nitrocellulose is a type of lacquer paint used in early automotive finishes. Not sure of the exact years it was used, but when I started painting in the 1960s, it had already been replaced by acrylic lacquers.
I would think any modern lacquer thinner would work for you. Acetone would also work but it dries faster than most lacquer thinners so working with the lacquer thinner may be a better option in your case. Either of those solvents do pose some risk to existing finishes so be careful. Avoid excessive dwell times. Dwell only as long as necessary. And definitely try a small spot before going crazy with it.
A safer alternative would be mineral spirits although it may not dissolve what you're trying to remove. It's worth a try though. That would be my first choice before moving on to the more aggressive lacquer thinner or acetone.
Another option, depending on the thickness of what your trying to remove would be to go at it with a polisher and compound.
Good luck.