I have a four post lift in my garage.You simply drive on to it then get out and press the up button.Attached to the lift on each side are very shallow ramps to drive over in order to drive onto the lift.The ramps are 2 inches in height to match the lift,flush with the ground at the other end and 18 inches long. When I try to gently drive up,the car will not move,it acts as though I shut it off.Even flooring the accelerator does nothing.And,no,it's not bottoming out.So back it up a foot or two,get it moving a bit and it will go over the ramp and move forward until the rear tires need to go up.Same thing.Back it up a couple feet,get it moving enough that the momentum takes over and then the rear wheels will make the grade. This shows me that from a nearly dead stop,the car will not find enough power to drive itself up a slight incline. I wonder how this would play out in other situations,like driving slowly through snow.
