My wife has a 2012 Camry XLE 2.5L with 128k miles on it. Around 125k she started complaining of the car “sputtering” when going uphill and idling more rough. I ordered Denso plugs from RockAuto and put them in and it cleared up the sputtering and rough idle. The car has recently started having hard starts when warm. It doesn’t crank any longer than usual, but right before it starts it’s almost like it struggles to start if that makes sense. Like it misfires for half of a second right before starting. In the morning when she starts it for work it starts up beautifully every single time! This leads me to believe that’s it’s NOT the spark plugs. We always use Shell gasoline for our vehicles from the same station. Any other things I could/should check?

 

So when the car is warm, it starts hard? Meaning the starter struggles to turn over the engine? Cold, starter turns engine over no problem and starts right up?
I suspect the starter. As starters age, they become hard to start when they get warm but preform great when cold.
Most auto parts stores will test starters for free as well.