My gold fish (comet) is in a paralyzed state in the morning, but it goes away?

As odd as it might sound, he could of had a stroke. animals can, anything with a brain can have a stroke. After having SBD, golds can suffer the after effects for a long time. It just might tanke him time to fully recoer. as long as he is eating well and you do your partial water changes as you should, just give him time to get better.