Macbook pro bluetooth headset auto re-connect doesn't work. Requires pairing after restart

I have paired my Macbook Pro running Yosemite with Bose Soundlink OE bluetooth headset. Once after I restart the mac, I need to re-pair the bluetooth headset. Mac wouldn't save it in the list of the devices like it shows my bluetooth keyboard and mouse.

I have opened com.apple.Bluetooth.plist and checked the list, the headphone is listed in the DeviceCache. The keyboard and mouse are listed under the PairedDevices. However the headset is listed in DaemonNoRoleSwitchDeviceList section. It wouldn't auto connect to the headset.

The headset tries to connect, the connected bluetooth icon appears on my mac for a fraction of second and goes off after which the headset's voice feedback replies - "Device not found"

Any idea what can be done to get it working so that the mac connects to my headset automatically after restart ?

When I have had this problem, it was always because my headset was paired to another device, probably my iPhone. I needed to explicitly unconnect from the current device before I could connect it to the Mac.

Likewise, I need to disconnect it from the Mac before I can connect it to my phone.

Some bluetooth devices can be connected simultaneously to more than one device, I hear. I wish I had one of those.

Now, what I want is to teach my Mac not to connect to the headset automatically, but only when I ask it to connect. (I don't want to remove it from the list of paired devices, because I do sometimes connect it.)