Congrats! From the start it have been your load shedding relay that have been the suspected one.
But then the ground connection for the coil via the starter, which is the most common problem with the LSR.
In this case it's the LSR itself which is the reason to the problem.....change it with #2 which is for the horn
untill you get a new one.....#1 is for the fuel pump and other FI related, so you need it to be able to start.
Other relays: left middle, bulb monitor...left rear, flasher...right middle, fan+temp warning...right rear, starter.
Thank you for the description. I'll try that. I'am also getting a new relay tonight from BMW dealer, I was lucky, they had only one left.