2013 Hyundai Sonata start and shift issues...

Recently, at times, my 2013 Hyundai Sonata fails to start when I turn the key
in the ignition and even when it is started it jerks when shifted into DRIVE.
The car will eventually start after several attempts, but the amount of
attempts or time it takes varies. This is a hassle because I never know if I'm
going to go through this and don't know if it will always be able to start. I
don't want to end up stranded one day. I've had the car checked out
thoroughly and no one can ever find an issue...battery, starter, alternator,
transmission...everything checks out well DESPITE having a transmission
code come up. I've even had transmission specialists look at it who have told
me that they've seen the same situation and code in Sonatas before but
couldn't find the real issue and refused to end up charging me loads of
money to try to fix the mystery and end up not fixing anything, because that's
what has happened with the same situation in the past. Is/has this happened
to anyone else and how was it resolved?