Why would apple ever build a car to start with ?
Honestly: most major car makers are or have given up on full autonomous driving (outside the USA and outside of Tesla). E.g. Mercedes Benz stopped development of self driving cars completely.
If I were Apple: that sounds like an opportunity.
Look at car component suppliers like Bosch, Brembo, etc.: they supply not just one brand, but will gladly supply all of them.
So instead of having to enter a market and compete for customems to buy an Apple Car, they could simply produce the needed electronics, sensors, and "brain" of the car and sell that to all of the car makers. That way if one were to buy in a few years a Beamer, a Merc, an Audi, or any other high-end self driving car: they'd get an Apple self-driving car with their choice of body shell, engine, and leather without Apple having to worry over any of it at all.
It would give Apple a much larger market share for the stuff they're good at: electronics, sensors, computers, software, ...
And leave the stuff like suspensions, bodies etc to those that are already pretty good at that.
Making the entire car is too prone to failure. Small steps always works better.
Making a self-driving systems that is foolproof around the world and can deal with unruly bikers, pedestrians, idiotic traffic rules, etc. is already more than difficult enough and has more than enough pitfalls already.