I did ask the vet. She said, it could be from an infection, she got from her mother before birth but the vet wasn't sure. She didn't give me a name for the condition. I'm supposed to keep an eye on it, see if it gets worse.
The symptoms have been the same since I got her, no change at all.
My friend, who also lives next door has got my kittens sister. The sister is perfectly healthy and normal, no tremors at all.
I probably love my kitten even more, with her little problem. I'm sure, she's in no pain.
I'd just like to know, what it could be.