My car is 2005 Chevy Impala. While driving in automatic mode, I have to drive at 18 MPH for around 4-5 seconds to allow the gear to shift from first to second (or second to third gear, I am not sure which gear). With a normal transmission, we can just increase speed from 0 without thinking about anything. What can be my problem? What is the cheap(money) solution to my problem?