Yeah thats what it sounds like look in the radio manuel for throttle reverse switch. By switching that it should change it so when you pull the trigger you now have throttle.
As far as turning the radio on before you turn the car on its so the car dont take off thats the reason for that.
If this dont take care of the problem let know the make and model of the radio that way someone that has the same radio will walk you thru it easy. Good luck...