What could be causing the valve rattle? on 2003 Nissan Pathfinder

When I turn on the car it sounds as though the valves are rattling. As I accelerate the rattling increases. It seems to drive fine but I am worried that there is a costly disaster waiting to happen because of the rattle.

Asked by for the 2003 Nissan Pathfinder
check timing belt or gas gate for fuel recommends premium fuel ...rattles if u use regular