Scene is from "The Wicked Dreams of Paula Schultz (1968) filmed on the sets of the "Hogan's Heroes" TV show with a lot of the same cast. Starred Elke Sommer who was always losing her clothes and was never quite (but maybe) shown nude. There's a thread and some stills
here and I uploaded a clip with possible ENF nudity at 0:43, 1:02, and 1:12. I've never been able to find the entire movie on youtube.