Why does my 1964 Cadillac start right up cold but after warm it starts hard

Explain a little more what you mean by starting hard. Does it start and run rough when it finally does start? Does it start up running smooth right away? Does it vary from one time to next? Does it ever backfire? Also you should run a vacuum check on it. This can tell you much about the engine. Here is a little diagnostic reference for vacuum on an engine.............................................. ......... You should get between 17-22 in. hg. depending on your elevation above 2000 feet MSL or mean sea level. To perform this test hook vacuum gauge directly to manifold vacuum. 1. Low steady needle usually indicates leaky intake, a leaky vacuum hose, late timing, or incorrect camshaft timing. 2. If reading is 3-8 inches low and fluctuates at that low reading suspect an intake manifold gasket leak at intake port or faulty injector. 3. If the needle has regular drops of about 2-4 in hg. at a steady rate the valves are probably leaking. (Perform a compression check). 4. An irregular drop or down flick of the needle can be caused by a sticking valve or an ignition misfire. 5. A rapid vibration of about four in hg. indicates worn valve guides. 6. Slight fluctuation of one inch or so indicates ignition problems. 7. Large fluctuation perform a compression check. 8. If needle moves slowly through a wide range check for PCV issues. Hope this gives you a good place to start and helps you figure it out.

THANNK YOU , you Have Givven me a place to start.