King snake weak and shakey

Question
Hi. I have a Chihuaha mountain king snake. Had him for .... six years now. I've never had any troubles with him. Good eater, friendly, all that. I went away for the summer and left him and my jungle carpet with my friend's dad (a breeder). I don't know if that had anything to do with this. Just thought I'd mention it. Although I did take a good look around and talked to him about it a lot before I left them and he really seems to care about his animals a lot and takes really excellent care of them.

The thing is, that since I got them back, my king seems to be quite weak. When I take him out he seems a bit shakey, like how you get after a really hard workout or something and your muscles aren't quite contracting right. I didn't worry about it too much at first, I thought maybe he just hadn't gotten taken out as much while I was gone. But he doesn't seem to have gotten any stronger since. It's not really bad. He still climbs around and can hold on when I take him out. He's still lively and curious and all that, just a little bit shakey.

He's refused two feedings (which he has never done before in all six years), but one was just before he was going to shed, so I am attributing it to that. I know two feedings isn't a lot to worry about (they weren't in a row), I just wanted to include everything.

I didn't really worry until I was sitting in my room the other day and he was spread out accross his cage and I saw him sort of spasm. Like a mini seisure or something. It only lasted a second, but his whole body tensed up and shivered pretty strongly for that second or two. I know tremors and lack of muscle coordination can be signs of neurological disease, but I don't know how it could have happened since he's always been healthy and nothing in his keeping has changed. Actually, That's not entirely true. I took my python to the vet for a check up and found out there were environmental (not reptile) mites in his cage so the vet told me to put the king on sand instead of the mulch I had him on at the time. And he gave me some stuff to get rid of them. I don't know if the sand or the mite stuff would have anything to do with it.

I just found this site (actually looking for plant care tips), so I figured I would ask before I take him to the vet. Just in case there's something I'm missing.

Do you think this could be something as serious as a neurological disease? Or am I overreacting? Could it be something else?

Thanks so much!!

Answer
That does indeed sound like a neurological problem. Whether it had anything to do with getting babysat, I am not sure. (Thank you for including all the back story. Saves me having to ask.)
Some neurological problems can be caused by some anti-mite devices that you stick to the top of the tank. I don't know of many that are in use nowadays but it might be worth asking your friends dad if he uses something like that.

Most mite medicine isn't strong enough to cause problems like that. And the refusing feedings happens occasionally, even in healthy snakes with no apparent reason. Frustrating, but happens.

If it is a neurological problem, I am not sure how much the vet can do. It would be good to take him in regardless to make sure that there is nothing else astray. You are right in  being worried, those are not minor problems.