I discussed this in another thread. One must hold the S5 screen open when starting the car with Bluetooth on. Then one gets a permission question on the S5 and one must answer YES. If one just keeps the S5 in one's pocket, it will not work with the car.
Evidently, the S5 has that security question to prevent one's addresses from downloading into cars not owned by the user of the S5. My old dumb phone did not have that question and downloaded all addresses to any paired car system.
The question could be answered NO. Then if one has others driving one's car or has passengers in the car, the S5 owner could prevent that information from loading for that one trip.