First of all, did you read the owner's manual?
Secondly, when these cases occurred, are you
absolutely sure you had successfully put the car into "Ready To Drive" mode? (The green dash light that shows a car with arrows under it.)
It is actually pretty easy in the FFE to prevent the RTD light from coming on. For example, if you aren't properly pressing the brake when you press the START button, the light won't come on. If you shift out of Park too soon, the light won't come on. Anyway,
this has happened to all of us, and usually because we aren't following the correct startup procedure.
Here is what I recommend for your FFE startup procedure:
1. Make sure car is in Park and the brake is pressed.
2. Wait a beat.
3. Press the START button.
4. Wait for the RTD light to come on.
5. Shift into gear.
It is very easy to prevent the RTD light by trying to move too quickly from step 1 through to step 3 (which I why I inserted step 2) and then step 3 through step 5. Let the brake to "settle" slightly before pressing START. And definitely wait for the RTD light before attempting to shift.
Anyway, once I had internalized the proper procedure, the "no-RTD-light" scenario rarely happens to me anymore. And, when it does, I am usually pretty darn sure it is simply because I went too fast. It is no longer a mystery to me.