Strange knock-like sounds from my engine

What is your question?

have you heard the sound that comes from MANUAL transmission cars when the gear is high on low speed and you try to accelerate or drive uphill? its like the pistons are rattling... my car is a AUTOMATIC kia optima 2015 and it makes this noise all the time it's like the car is too lazy to change the gears from 4 to 3 or 2 when i hit the gas on low speeds. two places when this sound is not heard: putting the transmission on manual and keeping it low (low as it SHOULD be) or hiting the gas pedal very very very lightly.

What makes this problem better or worse?

gets worse when engine gets warm

How long has your 2015 Kia Optima had this problem?

long long time