I have a 2014 Camry Hybrid and I just updated to the S5 on Sprint (previously had the EVO 4G LTE also on Sprint) and I am having the same issues with the Bluetooth... the phone will initially connect, but then I receive messages pretty much every minute or so that say "phone disconnected," "portable player disconnected," then "phone connected," "portable player connected." It drops calls if I get a call in my car and answer thru the Bluetooth system because it disconnects. It also does this with Pandora, it will be playing fine and then disconnect and totally screws up the app program in the car at the same time.
When I first got the phone, I was all excited to pair it with my car because I thought I would now be able to get text messages read out to me. I tried it in the parking lot with a friend and it worked great. But I only drove home that night and I was really close to the store. The next day I tried out the car mode on the phone to see what that was about and it drove me nuts and screwed up the regular Bluetooth in the car so I disabled the car mode. After that, I get the constant disconnect and reconnect. I wonder if the car mode somehow screwed things up?
I have unpaired and repaired and turned off the phone, pulled out the battery, etc. to no avail. I called the service center and they said that the S5 hasn't been tested with the system yet and there was no patch yet. Toyota Entune support told me that it was the first time he had heard of an issue with the S5 connection, even though it hadn't been tested yet.
My next call is to Sprint and / or Samsung to see if there is anything that they can do.