stalls at idle

I have a 02 ford windstar lx it has a 3.8 v6. When i first start it, it starts fine but after it warms up and i shut it off and go to restart it, it sometimes jumps around on idle. It will sometimes idle so low and crap it barley runs but after 1min the idle's right were it's supposed to and idles fine, I just bought it last year and have put on new serpintine belt new altinator,new motor craft plugs and wires, air filter,fuel filter,had the vacum lines on the back of the motor replaced 4 months ago they were deteriorated but i still cant figure it out any suggestions would be appreciated thank you.