Hard to start

I have a 2002 pontiac grand prix with a 3.1 engine it has approx 140,000 miles.
It just started to do this, but when I got to start the car the engine crancks real slow, I've changed the starter about 6 months ago and I think it might be the starter again, cause once the car gets started it will start up fine after, unless the car sits for a while.