Strange behavior causes?

I've had my dutch for about 2 years now and there was a bit of a scare with her last night- after I got her dinner, she didn't show any interest in it whatsoever (strange as the sound of the fridge door opening almost always brings her running), then after an hour or so, she went into a nearby corner that's not typical for her to lounge in and did the little rolling flop down and laid her head on the ground. I could tell her breathing became really heavy and when I went to check on her she wouldn't even lift her head from the ground. This had me in a panic and I called our after hours vet line, but in the 10 mins it took me to get a hold of the vet, she was noticeably better, up and moving around the house again. The vet advised us to try and get her to eat and keep an eye on her, which we did. I stayed up with her all night to watch her and her behavior is completely normal, she is dropping pellets, ate all her food and a good portion of hay, drank from her water bottle. I'm concerned what could have caused it in the first place and I am fairly certain she has been grooming herself to an excessive amount. I intend on taking her to the vet anyways in a day, and her behavior is feeling completely back to normal so I'm no longer sure how emergent it is for her to see the vet. Any thoughts or similar experiences?

It's really hard to say what might have been going on. It could have been just a stomach upset, though I've never had a rabbit completely lay their head down on these occasions. They will belly press but their heads usually stay up when they do this. It's possible it could be some other underlying health problem. If it is an underlying health problem, blood tests and xrays may pick up on it but they also may not.

Hopefully your bun gets a clean bill of health and it was just a bit of stomach upset.