This doesn't describe the experience I was getting at. I'm talking about actual conversations that I routinely have, not hypothetical ones I'm avoiding. It usually takes very little time to get to a point where the conversation just doesn't continue; I'm not trying to end it, it just sort of runs out of steam before it gets anywhere interesting. The disconnect might be that I don't seem to get any kind of mental/emotional jolt out of social interaction per se, which seems to be unusual.

Oh, you just have to bust through that. Say something else. Ask a question about a different part of their life.