I am starting at Amazon next week, can I drive to the shuttle stop on Monday and take it without any reservations prior? @Amazon
Depends on which stop you want go. Usually it is not a problem on the mercer island stops.
Can I show him welcome email or something like that? I really don't want to drive
This will probably work
Possible, but at the same time consider what are you going to do if they refuse to give you a ride. You don't want to be late on your first day nor do you want to be super stressed.
Depends on the shuttle. Your recruiter may send you an email you can show like you did for parking at an interview. In my opinion, it's a waste of time. Uber your first day and once you figure everything out you can adjust your commute by day 3.
I doubt it. The driver might want to see your Amazon badge.