iPhone XR camera starts shaking and makes a weird sizzling or crackling sound

My phone has had this problem since the day i bought it. It has to be the auto focus because if i put the camera in SLO-motion its totally clear no shaking or noise. See if its clear for you as well

It needs repair

iPhone Repair - Official Apple Support

or: contact Apple Support 

Anything other than Screen or Battery may be a replacement phone and the price is in the article under "Other damage"

You can see additional service information within the following article:

Prepare your iPhone for packing and shipping

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Oh dear. Only Apple can get hold of genuine parts, I don't believe many Amazon sellers are authorized repairers. Hopefully they only gave it a polish else if they fitted a fake battery Apple will not be interested in fixing it.

I would not touch a used phone with a long pole myself.