What makes a thought intrusive

So I was enjoying some “me time” and had intrusive thoughts, but it felt like just for a second I liked it. Like I’m holding myself back from “enjoying” the thought. And the thoughts are related to things I was into when I was younger, but sometimes I feel like I might still like it even though 9/10 I wouldn’t give it a second thought. Is this common? Or is this just denial? Thanks

I have been struggling today, most likely due to lack of sleep. I had a thought that I would consider intrusive, but what really unsettled me was that I felt like I liked it, **not just in the sense that I lacked anxiety over it, but that I genuinely felt like I wanted it.** It left me feeling really confused. It happened during intimacy, which makes it even more unsettling. The thought was incestuous, I found myself imagining and comparing the moment with my boyfriend to my father :/, and what really alarms me is that I felt like I wanted it there, both mentally and physically. I was having a really nice time, so maybe the physical sensations got mixed in somehow, but it still worries me. I did my best not to ruminate in the moment and avoided checking. I tried to move on, but the feeling of genuinely liking the thought was so clear that it is hard to shake off. Has anyone else experienced something similar? This is one of the first times it has ever happened to this extent.

I don’t know how to explain this so I’ll do it to the best of my ability. Does anyone experience “co-intrusive” thoughts that try to negatively support the initial intrusive thought? Example: Me: “Thank God I never acted on (scary intrusive thought) & I’m getting better!” Intrusive thought: “What a shame you didn’t” These types of things send me into a spiral. It makes me think that it could lead to a desire instead of staying a fear. Like an intrusive disappointment that I didn’t follow through with the thought? It’s been a long fear/obsession & I think my OCD is trying to trick me that the only satisfaction would be to act on the thought. (I know that’s bs) But IS that why it sends me the negative co-intrusive thoughts? That’s the only explanation that makes sense. Then I wonder is it something else? Am I a grenade waiting to explode??? I simply cannot relax in any moment because I think what’s the use if I’m just going to (xyz) one day?