Tail tucking when playing

In the last couple of weeks Saffy has started tucking her tail between her legs when she's playing with other dogs. She sometimes runs to me but most of the time just carries on playing. Was wondering if anyone's else pup or dog does this?
She's been to puppy classes and has been well socialized with older dogs, some we know and some we've met out on walks.
She doesn't seem scared, more excited but I am worried I'm not picking up on something and letting her get into situations she may be finding stressful.

usually a tucked tail is submissive/scared behavior, most likely she is trying to figure out the other dogs nature first and runs to you if she is unsure for reassurance
http://staffy-bull-terrier.co.uk/dogbodylanguage.html

When Loki was small and he'd never met big dogs before, the first few big dogs he met, he'd just stand there with his tail tucked between his legs, or a slight wag but still very much submissive. Then when he realised the other dog was friendly, he'd be playful and perfectly fine. Sometimes they get scared or unsure of things, so they'll take a moment to take it all in and observe it. If she's run to you, she was probably a bit scared in that moment and ran to someone she knows isn't scary, but if she's been fine after it, don't worry just keep an eye on the situation; if the other dog is fine, then she'll be fine.

Thanks So is it best to let her carry on playing then? When she comes to me as soon as the other dog loses interest she goes back for more.
Weird thing is though she'll go up to the other dog cocky as anything and initiate the play but then all of a sudden wuss out half way through

let them play, just keep a close eye on her and the other dog and be ready to separate them if needed

steve76 wrote:usually a tucked tail is submissive/scared behavior, most likely she is trying to figure out the other dogs nature first and runs to you if she is unsure for reassurance
http://staffy-bull-terrier.co.uk/dogbodylanguage.html

Would agree with this., she may be unsure of what the other dog is going to do next.

steve76 wrote:usually a tucked tail is submissive/scared behavior, most likely she is trying to figure out the other dogs nature first and runs to you if she is unsure for reassurance
http://staffy-bull-terrier.co.uk/dogbodylanguage.html

Agree with this and it should improve as she ages and gains confiedence.