Why Does My Car Start Better When It's Cold?

It;s an '86 Honda Prelude, and it has over 200,000 miles on it. In the morning it starts up instantly as soon as I turn the key. After it warms up and sits for 10 or 15 minutes it takes way longer to start. I've changed the fuel filter, plugs, wires, cap and rotor, and all the fluids. The previous owner had to get the (TW) temperature coolant sensor replaced, I've been told this could be the problem. I have the receipt for the new one and the sensor itself looks new. The car doesn't though any codes and runs fine after it is started.