The specific scene you're asking about involves Shizuka in a bathing or nude scene. However, such a scene does not exist in the original "Doraemon" manga or anime series by Fujiko F. Fujio. The series is aimed at a younger audience and maintains a family-friendly tone throughout. It's possible that you might be confusing it with a fan-made work, a parody, or perhaps another series.
Several Doraemon films feature unique variations of this trope that go beyond the standard bathroom setting: Shizuka Bathing Nude Scene In Doraemon
: Most scenes occur because Nobita accidentally (or occasionally intentionally) enters Shizuka's bathroom using a gadget like the Anywhere Door . The specific scene you're asking about involves Shizuka