I'd suggest either a fuel mixture problem or lack of spark.
Lean mixture has been suggested. What about rich and/or flooding? Is the choke automatic or manual? Have you tried starting with the accelerator held to the floor?
A lack of spark when cold can indicate an accumulation of moisture somewhere. Are you near the coast, so that salt-laden air might be an issue? A thin deposit of salt on plug leads or connectors, or on a cracked distributor cap or rotor can cause exactly this sort of problem. It absorbs moisture and shorts the spark after standing cold for some time, and behaves itself when warmer and drier.
John