Puppy Staffy limping on back leg no pain

Hi there hope you can help, I have an 8 month old staffy called Alfie,he is very energetic & gets plenty of exercise sometimes up to an hours walk, but recently he has started limping on his back leg but seems to be in no pain,he limps on it for a bit then is able to put wait on it again. He has had this problem before I rest him a few days then he is fine then out of the blue he starts limping again any advice please

Possible he could of strained it? i.e over stretched it or ran on it funnily? .. pups are mental and forever straining something! lol.
have you checked in his paw pads and between his toe's? also made his leg move from his hip etc? and pressed it firmly all the way up to see if he pulls away or yelps?

Yes tried all paw checks & pressed his leg all the way up to hip but nothing seems to bother him not even a flinch, he limps then is ok & seems to walk on it fine

do you give him attention when he limps? .. i only ask because my boy is a PRO at milking something that don't exist lol and some others on here have done it too! haha.
if he dont stop, id ring the vet ask if the vet nurse can have a look at him to be on the safe side.