Faculty-assigned MacBooks are not set to utilize domain credentials at this time. This means a local profile has been set for you to sign in to your Mac.
You should really never have to log out of your Mac, however updates will cause the Mac to restart facilitating your need to sign in. Your username has been set as your first initial.last name (i.e. j.smith). Your password is the one assigned to you by IT. If you opted to change your Google password, those two passwords do not match unless you have gotten with Keith to make them do so.