Does anybody experience certain moments or days with peaks of anxiety and dysfunction, but afterwards are fine?

I've been diagnosed with ADHD and Autism and I'm pretty familiar with the difficulties and increased anxiety/depression in day-to-day life.

Overall, I'm doing pretty well now. If people talk to me, they would not know I experience any difficulties in life. (Although I'm currently not working). I'm not really that stressed in general, I'm doing much better socially, capable of getting things done everyday, and not feeling terribly tired every day anymore.

But sometimes, seemingly unannounced, I get these bouts of severe discomfort. It feels to me like anxiety, but it's not preceded by any worrying thoughts. (as far as I can tell).

When I feel this, I usually have to lie down or I might start coughing and vomiting. And I will not be able to get myself to do anything anymore. (not even just do something I usually enjoy.)

This can last for an hour, but sometimes it's almost a whole day. Afterwards, I seem to be perfectly fine again.

Is this something that anybody else experiences? Or is there something else going on? Everytime I go to the doctor to explain this, they don't seem to be worried and tell me that it's probably fine.

But fear for having this happen again (And it seems to happen quite frequently), is what is keeping me from making any commitments in terms of my life or work.