If you are using AM system (default), you have to
1. readjust your transmitter to neutral
2. switch on both the car and the transmitter
3. adjust the small VR on the car's circuit board (PCB) so you can see the front wheels pointing straight
You should then have the steering angles even (if there is nothing faulty with your transmitter and the PCB)
If you are using an AD system, the problem you mentioned is probably caused by the KO or Futaba transmitter. You have to recalibrate your transmitter from time to time because the resistance of the VRs could have been changed due to ageing and wearing. To do this, go to 'set up' if you are using KO; go to'adjuster' if you are using 3PK.