My unit often can take 40 secs, or more, to boot, but I just accept it as part of it initialising and connecting.
By the time I'm belted in and RDMS turned off, Android Auto and Google Maps is normally almost there.
What I have noticed (Android) is that once the car recognises the phone and the phone gets the Android Auto triangle 'notification' in the top menu bar Google Maps launches in seconds.
When first powering up and the main infotainment screen has displayed, after pressing Start, I get the default 'Smartphone' icon display. Once it's connected to the phone 'Smartphone' changes to 'Android Auto' and again, within seconds Maps launches.
On some occasions I do press the 'Smartphone' icon that takes me to a sub menu with something like 'Phones ready to connect' and pressing the valid phone usually speeds it up.