2005 Dodge Caravan Hesitates between 35 to 45 mph

Hello- I have a 2005 Dodge caravan... we recently started noticing that when we drive the vehicle in the 35 to 45mph range there is this strange bucking or hesitation when you have your foot steady on the gas. I had one of my buddies hook up the computer diagnostics to the car and he found no errors in the computer system for the engine or transmission or anything. It feels like if you were driving the car let off the gas and stepped on the gas again quickly. But at a high frequency... like every second or two. Lost on this one, I heard fluid, new trans, fuel filter, trottle cable.
Any help is needed first time user of site.