My 2004 pontiac montana 3.4 starts fine when its cold but after i drive it and vehicle warms up i can can shut off and try to start but takes several cranks until it finnaly starts. If i leave it for several hours it will start right back up ???? Ive replaced the fuel pump. Idk where to start now??

First check for codes even if the check eng light is not on.
Try unplugging the mass air flow sensor when its hot see if it starts right up then.

I had a similar problem with my Olds 88 with the 3800 motor. Once I replaced my Fuel Pressure Regulator she ALWAYS started right up.