Horse is an old TB, semi-retired, but still does some basic dressage and short trails. Horse is hot, very hot, and sensitive, not a beginners ride, fairly easy keeper, especially considering age, lack of teeth, and breed.
The other day I watched horse sunbathe standing up. Started to wobble a bit and then seemed like she woke herself up. This happened several times. I realized that I never see the horse lay down outside (all the other horses do) and I very rarely see shavings on her in the morning. She gets up and down to roll just fine though. After watching the horse get all wobbly and almost go down to her knees several times, she actually fell all the way down, straight down and onto her side. She started twitching/moving her legs a lot. I've seen my gelding move his legs when he dreams and this was much more violent than that, it almost seemed like he was having a seizure of some sorts. I wasn't sure what do do, I didn't want to spook her or put myself in a dangerous position so I got about 10 ft away and started clapping and yelling to see if she was at all aware of me. When I did that she promptly got up and trotted off, chasing one of the geldings and going over to eat hay. I was so confused by the whole episode I didn't know what to think. I watched her for another few hours, took temp, checked respiration etc etc and she seemed 100% fine. I kind of got it into my head that she must not be sleeping and got so tired she just fell down and fell asleep.
Then today (several days later) I watched as she seemed to stumble/wobble again before "waking up" only this time she was eating hay. Afterwards she seemed 100% fine. So now I'm very confused and have no clue what to think.
Im not sure if this is a vet ASAP kind of thing or not. We have opossums, deer, fox, raccoons, etc in the area, she is UTD on shots.
Definitely discuss with your vet, but I would totally presume narcolepsy before you panic, and then if that doesn't seem to be the case, then worry about other neuro stuff. I had one who went through two bouts of it, the first time was terrifying as he would randomly fall asleep while fully tacked, including falling to his knees on a concrete aisle. Changed his turnout situation (the general wisdom is to put them out with a bitchy mare who will make them feel comfortable that someone else is "standing guard" - that wasn't an option with this guy, but we did move his paddock) and it was fixed like magic. He had been with me for 5+ years at this point, and from a "people" perspective, there was really no logical reason for him to suddenly not be sleeping, but that's exactly what was wrong.