Had my xterra to Nissan under warrantee for this issue they changed the lifters,guides,rockers problem solved until one year later happening again still under one year with the dealer bringing it back. I was given no reason as to why this keeps happening. Does anyone know

lifter chatter at startup is fairly common. Should stop once some oil makes it's way up there.

Wait until you hear it in the winter! Mine was LOUD from day 1.

Make sure your using an oil filter with the Anti-drianback. Thie will keep the oil closer to where it needs to be and cut down on the clatter a bit sooner after startup.