Your grandparents did it and your parents, and that's how you came into this world. Sex is one of the basic human needs, along with food, water and shelter. There are shows and movies with plenty of sex like"Shameless" and "Californication". Those types of shows are awkward to watch, especially when your family comes in the living room and you had zero idea that you were going to see naked David Duchovny having sex with a 20-something girl. That might have been too specific, but you get the idea. No one knows though that sex scenes are very technical. Especially after MeToo movement.
Learn to be comfortable when you’re uncomfortable. Especially if you have a sex appeal and audition for a lot of scenes that require nudity or stimulated sex scenes. Three of my biggest auditions involved having sex. Two of my biggest paychecks involved nudity. My first naked gig was a body double. Was I uncomfortable? Absolutely! Was it rewarding? Yes! Was it empowering? Hell yeah!!!
After #metoo movement started, more jobs of intimacy coordinators began to open up. Intimacy coordinator regulates, explains how the sex scenes should go, he/she makes sure both of the actors are comfortable doing them, they also take actors' robes right before cameras start rolling.
When I booked my first co-star I had to do a sex scene. Both me and my fellow sex parner went into details with an intimacy coordinator and we had fun! The scene was funny and no one got hurt- physically or emotionally. I was surprised at how comfortable I was while walking naked in front of strangers. But I guess I was "in the zone", called acting :)
You can tell your agent that you're willing to do simulated sex scenes and/or nudity, but you don't have to! REMEMBER THAT. You're your own best advisor. But if you decide not to do them- more job opportunities for someone else.
You get more comfortable the more sex scenes you do, trust me on that one! And you get your confidence on a brand new level. As tasteful as sexual encounters look on television, it’s very technical and weird. But boy- it is fun!