I dont drive my car hard, in fact I dont drive it much at all

Its an automatic so it can't be the clutch

some more background info, the climate I live in is hot! I live in key west florida and the heat index sometimes gets to 110 degrees or so. I only drive my car like max 15 miles a day cause where I live is so small.

my brakes look good, no fluids visible.... could it be something to do with sparkplugs? just wondering