As a mechanic and a 182 owner myself, that sounds to me like the dephaser is on its way mate to some degree they rattle but that is more than id class as exceptable , its not normal noise but very common and needs sorting its a cambelt off to sort out as its driven by the belt ( i would recommend putting a full belt on kit while your at it and so would most good mechanics)
Id get it done sooner rather than later as yes it goes drive and its just rattley but if it gives up completely it could spell disaster and you dont want to have to pay for a engine im sure !!