Hi Vianney, not sure if you've sorted this yet or not, so apologies if I'm late to the party. I've recently experienced the same issue with my 2007 4.4 V8 Aero. Turns out that the factory incorrectly labelled some of the fuse boxes and the Fuse for the Starter Solenoid is shown as a 20A whereas it should be a 30A. I've changed the fuse from a 20A to 30A and the Aero has started on the button every time since. Fingers crossed this works for you too, if you've not yet found this solution.
