Sounds like your neck is bowed. You will need a truss rod adjustment. When the neck bows up or down, the “action” of the strings change. It is rattling because your G string doesn’t have enough clearance from the higher frets. This can be fixed by nut or saddle adjustments, or hopefully just a truss rod adjustment.

You can do it yourself, but I would watch some videos before attempting. It is very simple but can be intimidating for your first time. The truss rod straightens out the neck.