What might cause Kia Stinger rattle noise?

There are a significant number of issues that would cause Your Kia Stinger to rattle while driving or at idle, but most commonly it'll be the result of a suspension component. Try to isolate where the sound is coming from; if it can be traced to a specific wheel or axle, investigate the suspension components there -- including struts, shocks, ball joints, sway bar end links, etc. If it's an engine rattle, it's also possible that Your motor mounts have gone bad; this is more common when the rattle persists at idle. The normal operation of the engine is enough to cause back and forth momentum, and if the motor mounts aren't working properly, this can manifest as a sort of "clanging" sound, or perhaps the "rattling" which You describe.