Don't worry, my hamsters do this all the time.
One of my hamsters washes his face way too much that the fur on his face become a little wet. He would lick his paws and wash his face rapidly and scratch with his hind legs. I find it cute and funny. I would see him scratch every now and then while playing too.
Also, I don't think they feel itchy, they just love to keep themselves clean and it's normal and natural for hamsters to scratch a lot.
But if you notice your hamster is scratching WAY more than usual, and has flaky or red, irritated skin, or see patches of fur missing, you might want to see the vet. Your hamster may have a skin infection or mites.