How can I get Windows to start the Serial Monitor window after a restart? Is there something I have to copy into the Windows startup folder for my account? Thanks
You can't. You would need to have some way of telling the Arduino IDE to open the serial monitor and connect to a certain serial port. That can't be done.
Instead you would need to use some other third party serial communication program. How you would configure that depends on what the software is.
For Windows 10 you can make a program run at startup by following these instructions. You still need to configure the software to automatically connect to the right port at the right speed, of course.