So, I dunno if it's still around but there was a fantastic mini tutorial bunch of blog entries by an erotica author I can't remember the name of but I read it a lot years back when I wrote a lot more sex scenes then I do now called How To Be A Sex Writing Strumpet. Some of the main things were that unlike a lot of writing, sex scene can have sentences full of flowery language. One of the main things is to read it through and have it flow. Stop thinking about the rules of writing so much and try to just get a scene that moves. Also, that a focus on foreplay is generally considered better since most people reading sex scenes, especially if you're specifically writing a romance genre/subgenre are women, The actually intercourse itself should be kept someone around 500 words (as a rough guide) or it'll drag too much. Unless you're specifically writing a slow burner, it's recommended you don't leave your first sex scene any further than a third of the way through.
Also, and perhaps my favourite, don't be afraid to have the sex scene interrupted/messed up. It builds tension, but also humanises. One of my favourites recently was a character with super strength breaking the window he was leaning against in the middle of the sex scene. It has readers and characters going "they were so close aaaaaah" but also "omg that was hilarious". Bad sex happens, don't be afraid of it.
And also, as with any writing, if you're not feeling it, your readers probably aren't anyway.
And as always, the ultimate resource for writing Jenna Moreci has some great tips, which is obviously kinda NSFW just by the nature of being tips on writing sex: