I turned off the engine but left the keys in the ignition for about 15 minutes (while i took a nap). I suspect the key wasnt moved fully to the 'off' position.
After about 10 minutes, I started hearing a repeating 'clicking' sound. Possibly it was trying to repeatedly fire the spark plugs? After removing the key fully, the clicking sound continued for another minute or so before stopping.
Right after this, the car wouldn't start at all. (no sounds)
I left it for about an hour and tried again, this time it chokes a little bit, but fails to start.