My 2005 Kia Optima will sputter just a little.

My 2005 Kia Optima will sputter just a little then stall out while driving, sometimes it will crank right back up other times you have to let it sit for a little while (15-30 mins) for it to crank again. We have taken it and had it placed on the computer, no error codes were given, they also checked the fuel pump pressure and said it was fine also. Any ideas?