I've had snakes that have a huge issue with the carpet your using in its enclosure. Also, the bird... I know you say its been there for some time but your snake could be stressed over it and it just cant take it anymore. Its probably a really good sweet snake when your handling it and may not show signs of being stressed but it really is. For the sake of discussion just try moving it out of the room. yes, it does look like its having seizure. Those can be caused from prolonged stress especially if they just started happening with in the last couple months. Did i see a snake bed under the hide as well. I've never seen that either maybe take that out as well.