It does that sometimes with me too. When it happens I find completely disconnecting/deleting the paired equipment from both car and device then pairing again sorts it (until it happens again...).
Paired mine 5 years ago, works every time I get in - RT6 (a bit of a lie actually, I swapped my iPhone 6 for an iPhone X when they came out & had to pair that one, but you get the gist).
Me too had no issues with any of the Z's RT6 and NG4, though NG4 did take it's time to connect - sometimes.
Laugh and the whole world laughs with you.... or is that at you?
Former owner of Dolphin Blue GT200 fully loaded inc. Quads / Xenons. Now on second white* R currently sporting an AveryRoaring Thunder Gloss flip colour wrap.