Sif is starting to scratch himself on the bars of the cage
I have never seen Sif act like this but he mows everyonce in a while will go on the back part of his perch and will rub his whole body against the cage and even moves his head around scratching himself is what it looks like idk I haven’t ever seen him do this and I don’t know if its something I should be worried about or not I’m a new bird owner so I might be worry for no reason
He's just having a scratch. He may be starting to moult which makes budgies very itchy and scratching helps them not only to ease the itch, but also to get the old feathers out, ready for the new ones to come in.
Nothing to be concerned about. It sounds as though Sif is starting his molting process.
Take the time to read the stickies and budgie articles and you'll find most of your concerns have already been addressed.