Ok…I read the other discussion about the Master Warning coming on, but in that case, the owner was experiencing the probliem in cold weather. WE have mostly experienced that same problem when the weather has been warm, the issue mostly occuring when the ambient temperature is above 85 degrees. We have taken the car to several shops, including the dealership, and the error code they have retrieved from the computer indicates that the Mass Air Sensor in the air intake needs to be replaced (at a cost of $110.00 to $135.00 P & L, depending on who does the work). Unfortunately, replacing the sensor DOES NOT fix the problem! We are now on our fourth Mass Air Sensor, and we have discovered, by patient (if somewhat annoyed) trial and error that if we simply disconnect wire to the Mass Air Sensor from the system for a moment and then reconnect it, the vehicle starts right up, and cyclying through 2-3 starts also resets the warning lights. We are now doing this with the reluctant but agreeable endorsement of our local Toyota dealer, since they have been unable to solve the problem any other way themselves. We would LOVE to hear from anyone else who has experienced this problem, and whatever they have found actually FIXES this issue!