I see that Sadie is a tortie, from the pictures in the post header.
I know "tortie" isn't a breed but our, tortie, Kasey does a similar thing.
Kasey purrs but she will make a weezing or moaning sound when at rest, sort of like an augmentaion to purring.
I had her thoroughly checked out and everything is fine. There may be one difference from Sadie in that she can stop the noise at will, at any time, when distracted, petted, sees a toy, hears someone in the kitchen etc. If it were a respiratory problem or other health issue, I don't think she could stop the noise.
Originally Posted by Tiffany01
I even wonder if it might not be a self-comforting habit she developed early on.
I think in Kasey's situation, this is what is happening, I rescued her from a location where she never knew what people were going to do with her, from one moment to the next.
Oddly, my wife had a visitor today that said they had a tortie that made some unusual sounds too.
I hope you can get it sorted out and all is well.