I always recommend 'Call Me By Your Name' for this. The scene by the peach tree isn't there just for shock; it's this raw, messy, intensely vulnerable moment that completely dismantles Elio's intellectual posturing. You see his desire, his shame, his curiosity all crash together. It’s awkward and beautiful because it shows his character turning inside out, moving from theory into overwhelming, messy practice.
For something different, 'The Kiss Quotient' by Helen Hoang has a scene early on where Stella, who's autistic, meticulously plans the encounter. The writing focuses on her clinical checklist dissolving into unexpected physical sensation and emotional connection. It's not about the mechanics; it's about her losing that rigid control she uses as armor, which is a huge developmental step for her. The sex directly progresses her relationship with Michael and her understanding of herself.
Molly from 'The Flatshare' by Beth O'Leary comes to mind, too. After escaping a gaslighting relationship, her first time with Leon is fumbling, and they stop. The narrative weight is on the aftercare—the talking, the laughing, the making toast—which rebuilds her trust in intimacy more than any perfectly executed scene ever could.