I remember some people here describing something like this. Like they normally can't visualize, but on the rare occasion that they do, they can barely hold on to the image before it ends up like what /u/margobisbee posted.

A different version of this happens to me when I take Ativan, the first few hours are okay, and then I find that I can't hold onto my thoughts. Like I can't visualize to begin with, but now say I just want to think of an apple, not even the image of an apple, just the concept of an apple. Well, I can't hold onto it, my brain will just be like 'fuck your apple, here's a dog, and here's a train, and here's some random shit you don't care about, tralala.' (This is not literal, I'm just having such a hard time verbally describing what happens because there are no images, but the concepts themselves are so difficult to hold onto, it feels like my brain hurts trying to force myself to focus on APPLE and just hold onto it while it feels like my brain is trying to pull the concept away from me and discard it) I considered it a version of an intrusive thought when it was happening to me because there is that miserable/discomfort feeling that comes with it. Like, holy shit, just let me think of my apple in peace, why am I being forced to think about a banana instead?

So... yeah, I avoid taking Ativan unless absolutely necessary and try to be asleep before this portion of the ride happens. It's very agitating.

I used to have actual intrusive thoughts a lot (I have CPTSD) and I think a lot of it had to do with medication I was on. If you are on anything, you might want to discuss it with whoever prescribed it to you. I also had this thing called 'ruminations' which are like intrusive thoughts on crack, but I worked through those by actively 'pushing them out' and rejecting them every time they popped up, which, at the worst of it could be like a thousand times a day, now I can go two weeks without getting even one intrusive thought/rumination, and one slips through, I catch it right away and go 'Nope! This is a rumination and it needs to fuck off!' and I just push it out of my brain. I know I'm making it sound easy but it took a lot of hard work to get to this point. I hope this helps you in some way...