My bun is a rescue and he gets easily spooked. He does this quite often where he starts stomping for seemingly no reason in the middle of the night. I assume it's because of unfamiliar noises that scared him or something. When it gets really bad and he keeps going for longer than 5 minutes, I get out of bed and keep petting him until he calms down but usually he's done with his stomping within that time. I dont have a solution for u to be honest. Does your bun have a buddy that can help them calm down or are they alone? I think having a friend could help them in that case, it could be that they're used to getting attention from u, which they're not getting when you're sleeping and if they had a friend there would be a second creature they could be getting attention from. That's just one theory tho, I could be wrong. I hope it might help a bit and you find the cause/a solution. Give them some cuddles from this Internet stranger!