starter heating problem

2001 mustang gt,50,000miles. When my cars engine is cold like in the morning it always turns on with the first try. When engine is at normal operating temperature and i try to turn it on it rarely does and all i hear is a click and no start. I put the car in 4th push it forward then it turns on. My friend said something about aligning the flywheel to starter.Thats the way it turns on and im trying to figure out what to replace. thanks