Engine problems of the 2002 Lexus ES300

I recently purchased a 2002 Lexus ES 300 and not much to complain about the inside etc. The acceleration and throttle though are a major problem. I almost got into a car accident getting onto 95 trying to pass a semi because the accelerator " pauses" when I step on the gas pedal. After the pause it starts to accelerate so I barely made it without hitting the semi. This really concerns me and want Lexus to do something about it. Its just plain unsafe.