To use your Bluetooth® wireless technology enabled phone in your vehicle, an initial one-time-only pairing procedure is required. To pair your phone, initiate Bluetooth® search mode in the vehicle. Then depending on the handset, initiate search mode or discoverable mode.* Once the vehicle finds the handset, a Bluetooth passkey is required to complete the pairing procedure.
You may choose any combination of 4 to 16 digits. Enter the passkey on the phone or vehicle, as prompted, and then the other device will ask you to verify it.
If it really is a 2006 or earlier year 335i Coup?, you need the vehicle's Owner's Manual. Since: "Vehicles require a fixed Bluetooth passkey for verification which is included in the vehicle's Owner's Manual."
You can obtain the manual from the dealer, when you provide them with your vehicles VIN-code, for a price of course.
From the BMW USA site: