Tigger's unusual behaviour

[Phoenix]

Ive noticed right from when I first got Tigger that when she's snuggling down and kneading away on me she'll rub her head against me then start acting like she's got food trapped in her teeth when she hasn't (she tilts her head to one side then uses her tongue in her mouth like there's food wedged in her teeth when there isn't (and she's got nothing wrong in her mouth, the vet checked her over when she gave Tigger her booster). Tigger's the only cat I've had who ever did this behavior - any ideas why she does this?

Shame the video on my camera's not working or I'd try and get a video of it to show you what I mean :?