Cat is quivering and her meowing sounds shaky and crackled...

I just adopted my female tabby in November.  Great girl... this morning I noticed she spit up a little.  I didn't think much of it.  I then seen her in the window, starring up a bird.  She was quivering, though.  Her whole head was shaking.  When she mowed, it wasn't smooth like normal, it was crackled and shaky.   Is she ok, what is going on?  She seems fine now but what was that all about?

Could she have been chattering? Cats usually do that when they see potential prey that's out of reach, usually birds. Was it similar to what this cat is doing?

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If she continues to spit up, acts lethargic or shaky, she should be seen by a vet, just to be on the safe side. Is she eating okay?

Actually the meowing was similar but she was shaking unlike this kitty. She has been eating normal and acting fine this afternoon. I will def take her to the vet if it continues .. just scared me!  Thank you!