You might just want to try a Hard Reset before you call the tow truck, (actually flat bed because you sort of cannot tow due to All Wheel Drive.)
Well you can flat tow with all 4 on the ground but there are rules so ....
In brief, to start the hard reset process, open the hood but close all doors and let your 3 go to sleep - no radio display etc.
It is often a good idea to have a window rolled down and the key in your pocket whenever fooling about the vehicle.
Disconnect the ground battery terminal from the battery.
Disconnect the positive battery terminal from the battery.
Connect the negative cable to the positive cable. (NOT the battery.) You will need a short length, (a foot or so), of light gauge, (14 to 18 gauge AWG, stranded copper), wire to do this as there is not enough slack in the positive and negative battery cables for them to touch each other.
Hold them together for about a minute or so, (some say 5 to 10 minutes); you are discharging memory modules within the engine computer and elsewhere.
Reattach positive terminal to the battery.
Reattach negative terminal to the battery.
Try to start engine - well it might, but probably not. Since the problem is intermittent, the hard reset erases of some of the trouble codes.
You will still have to have the dealer solve the problem, but maybe your 3 will start just one more time.
This is a link to a thread in disco3 re hard reset.
DISCO3.CO.UK - View topic - Hard Reset