is moodiness common in cats?

Question
I have a 3 year old female mixed maine coon cat whom I picked out from the shelter 6 months ago.  Sometimes she would sit next to me and purr while I pet her but then she would suddenly stop purring and would instead start growling.  Is that normal?  She is my first cat, and her moodiness is stressing me out.  Thanks!

Answer
Hi Mary,
I'm not sure why she would do that. It could have something to do with her background before you got her. She may still be learning to trust you. I would take it slow and continue to give her lots of love and attention. Sometimes cats from shelters come from abusive backgrounds, so it may take longer for her to trust you completely.  I think if you will give her time, and be patient with her, she will turn out to be a wonderful pet.
God Bless,
Becky