I have a 19....Happens to me all the time..
I'm an actual developer and so I have all sorts of tricks to try. So seems like there are three sets of issues:
I have the latest software version for iPhone X, Software Version 13.3
Just a note: Seems like the more updates from Apple the worse it gets.. I could be wrong, but that's what it feels like.
1. The iPhone is locked. Solution: Unlock phone
But then just to mess with me, it seems to think it's fun and games to startup and look normal and then freeze. So I can't select anything on the screen (console in truck, not iPhone). See unresponsive console below for behavior.
2. While truck is starting up ,plug iPhone in (which is unlocked) and put transmission into reverse (getting backup view) and then back to engage Drive on transmission and then screen is locked up.
3. While driving (short distance, usually I've just pulled out of parking lot) and plug the phone in, SYNC3 just ignores it.
** BUT I'VE HAD SYNC3 just freeze without iPhone **
This is what I call the unresponsive console.
So it can be cold or hot, rain or dry, humid (well as far as SF Bay Area Humid) it doesn't matter.. this damn SYNC3 freezes from time to time. Where you try to switch Sirius XM channels (preset) and it won't let you. If you try to switch to AM/FM that works but the user interface doesn't update.
So I'd day overall this interface SYNC3 (or 4 or 5 whatever version I have now) sucks. My 2013 had SYNC2(I think) and it worked flawlessly. Never had an issue....
I know not alot of detail but I think we can all agree that these guys have some bugs to fix.