If the kittens are are particularly young, shaking or trembling is a normal occurrence. Young kittens tend to shiver when they are cold, so it is recommended that they are checked and provide them with extra towels and blankets to help them stay warm.
Some cats will purr so loudly that they make their bodies shiver, or will shiver when petted or particularly happy. This would likely be similar to when a cat's tail trembles when it is excited or happy, but happening to other parts of the cat's body instead.
If your cat doesn't seem to be in pain, or doesn't have any other changes in behavior, it is probably nothing to worry about. Do keep in mind, however, that cats will sometimes purr when they are sick, and if there is anything different about your cat, due as changes in behavior or daily habits such as eating, it may be wise to take the cat to the vet for a check-up, just in case.
The animal is content and happy
It means that you enjoy spending time with kittens, the look of kittens ect.
It is probably purring but if not, you might wanna take it to the vet
that theyre beutiful
"Shake your shillelagh" is a playful expression that means to have a good time or party enthusiastically. A shillelagh is a traditional wooden club from Ireland, so shaking it in this context is like dancing or celebrating with energy and excitement.
Ignor them, or if theyre being immature, give them theyre own medicine.
This is called bruxing, and it has a similar meaning to a cat purring.
you know just shake it
She is just greeting her kittens.
theyre in their menstrual cycle
theyre rich.
It means that the cat is purring very loudly, like a boat's motor.