Using the BART schedules, you will see you have to make one transfer, and use a bus shuttle at the OAK end of your trip. Not exceptionally convenient if yo have check-in luggage. N.B. The schedules vary considerably weekdays and weekends.
Once upon a time

they actually had a super service - ten minutes or so - SFO Helicopter Airways! I used these a few times, what a convenience! :sigh: