Why wont car shift into gear when cold?

manual stick or auto? manuals are picky about having their fluid warm enough before they like going into gear. autos have shift solidnoids* that STICK after they collect some miles. The fluid prolly needs to be changed.(My god, just do it people-old wives tale about not wanting to change is ok/better) There is also a pump on the inside of the trans of an auto that builds pressure, this may take time" pump up" enough pressure for things to being acting normal.