All of a sudden, the Bluetooth connection on my 2009 IS 250 does not work automatically.
In order to get my phone to connect, I have to do one of two things:
1. Unpair the car from the phone and then re-register the phone through the car's interface (re-enter the passkey)
2. Delete the phone from the car's interface and then re-register it

This just started happening in the last two weeks (I've owned the car for almost a year and had no troubles).

Not sure if it is with my phone or the car -- the phone doesn't seem to have any issues with any other Bluetooth device so I am leaning towards something with the car.

Stats on the phone: Samsung Galaxy S9+

 

I also have a Samsung phone (Galaxy A8) and have occasional problems with Bluetooth connection to my 2015 ES, problems I did not have with my old phone, a Blackberry.

I find that in the cold of the winter, the phone will not pair with the car, but it will pair some time later, after things have warmed up (phone or car, I don't know).

I also found that there was a pairing problem with a battery management app I was running. I installed the app when I first bought the phone, allowing me to run different battery-saving modes automatically (such as turning off WiFi or Bluetooth) depending on location or time of day. It worked at first, but then as updates were loaded on the phone, the pairing problem started to appear, sometimes randomly, it seemed (I do not know if the problem was caused by Samsung's Android updates or caused by the app's updates). I stopped running those battery-saving modes and that pairing problem is now gone.

I also found that sometimes my phone would switch off features (such as Bluetooth) itself (perhaps switching off when no signal was detected) and then not automatically switching it on again, so that I would have to go in and manually switch the feature back on. The latest Android update seems to have taken care of this problem.

I am not completely satisfied with Lexus' Bluetooth system because it does not seem to be very stable; the Bluetooth system on my wife's Honda Accord seems better -- it can pair with 2 different phones which the Lexus system cannot. I was also not completely satisfied with my Samsung phone (but, cross my fingers, seem to be fixed now). I believe the problems I have had, though, were caused by the phone, not the car, as I did not have the problems with my old phone.