OK, I love this question...
1st, if the spark plug is not new, replace it with the proper gap setting..
We want to give the engine every edge possible to start when cold..
I fully believe you are looking at a Fuel delivery problem..
Warming up the engine makes it easier for the spark plug to work because the fuel is warmer and is closer to being in a vapor state..
Also, all the parts that the fule touches are warmer moving it even closer to the cumbsution point.
The spark does not have to very HOT to ignite warm fuel..
Take this to the extreme.. If you leave an old car in the Snow, then try to start it, it is very hard to start, when it warms up it is much easier..
Oh WAIT.. You live in Florida, what do you know about snow..
ANyway, the above also has to do witht he OIL warming up to and making the piston rings seat better, and the cylinder seat better.
SO.. It is Possible you have Low compression caused by bad rings, worn bore, mist adjusted valves or ones that do not seat properly..
You can test the compression if you have a tester gauge..
BUT, most likely I think it to be a carburetor problem where the carb is not perfectly working.
Some of the tiny holes may be plugged. When the heat makes the expand, the gas floes better.
Also you may have OLD Gas...
There are more detaisl to follow.