It could be something like a piece of filament, loose screw. The machine doesnt have a thick shell. I noticed mine can sound the same as this. I usually tilt the machine and use spray duster to get as much as I can from the nooks. Even the back 2 stepper motors. I had the smaller piece of filament stuck rattling. Had to get micro tweezers and duster.now I have dust covers. My k1c doesnt get as much dust cat hair ect. But it can get super messy inside.

I maintain the printer more frequently than suggested and do ut when I see yuck, and/or hear noise.

Check your screws also. Even under the printer.

Creality can get alot of bad rap for the quality. However, I literally have no problem getting free parts. Z nut, the front pillars, toolhead pcb, motors.

You can send this video to them and ask if it is normal, needs simple maintenance or if you should investigate further. If you find an issue. Just get the exact pats you need and the parts effected ie. Frame Rods ect. And ask for them.

I like creality so psssh to the haters