Focus 2010 2.0 TDCI

Had this light flash on when driving now and again, it became more often and has now gotten to this stage where it's a struggle to start the car, I can hear a relay clicking when the light is flashing.

I've changed the keyless fob battery (even though I don't think it's the problem as the dash says when the battery is low) but it makes no difference.

Video is here: