My first guess is that she is having complex partial seizures relating to the Cushing's, and gets some kind of aura that makes her feel she should lie down ahead of time. I guess if that is the case, I'll just monitor her as long as she doesn't progress to having grand mal seizures. If she does start those, I would have to put her down to keep her from going out in a bad way.
Are there any other explanations? I was considering a few things...
-Since this is around feeding time and her teeth are getting worn down (she just had her dental float recently and still has chewing surfaces, but the teeth are short): I wondered if she could be getting some kind of wad in her esophagus that caused pain as it went down. Maybe this pain would make her want to lie down until it passed, and the staring off and twitching is related to focusing on that.
I have seen her have to cough up a wad of hay a couple of times in the past several years. I'm there when she eats most nights though, so it is a rare thing.
This one I think is unlikely, judging from how horses and donkeys normally behave when they choke, which is not to lie down, but to stand rigid craning their necks and trying to swallow; and I've not seen them go down with that, even when obviously sweating in distress. Plus, no such behaviour ever from Romeo - neither typical choking behaviour or what you are describing - even though he was cudding and spat out about half his wads towards the end of his life. (For anyone who hasn't seen it, horse skull with no teeth left in bottom jaw here: https://www.horseforum.com/member-jo...post1970764997
PS: Having read your subsequent explanation: Well, there's another example of individual difference in responses! I've seen quite a few chokes, including a near-terminal one when the first vet didn't remove the obstruction, but only push it closer to the stomach, but had never seen a horse with choke lying down!
-Some kind of intermittent heart arrhythmia that causes her to feel strange or have chest pain, so she lies down until it goes away.
Feeling faint, for whatever reason? Episodes of low blood pressure, given that Cushings can affect a lot of homeostatic mechanisms?
Is she ever sweating or showing other signs of serious pain with this? (ask I, at n= 2 here
) ...dizzy or woozy would be more my guess than pain, but how's her coordination going down and coming back up?