No Strings Attached (2011) on Netflix

Adam (Ashton Kutcher) and Emma (Natalie Portman) met each other once at a school summer camp but never committed. Several years later and they meet again. Adam is now a writer and an assistant on a TV show and she's a nurse. When Adam discovers that his father Alvin (Kevin Kline), a washed-up actor, is having a relationship with his ex-girlfriend, he goes on an all-night bender. Waking up in Emma's house, he finds comfort in her and they have spontaneous sex too. They decide that they should restrict their relationship to this level as she isn't comfortable with dating. She decides to keep it a secret from her housemate's Patrice (Greta Gerwig) and Shira (Mindy Kaling). Typically, Adam feels left out by this demand and tries to develop the relationship into something more with the help of his friends Wallace (Ludacris) and Eli (Jake M. Johnson).