You may have a problem with your Apple or Windows computer where you startup the computer and it will hang on startup. With Windows computers, this may happen immediately after the POST (power on self test screens). With an Apple computer, this may happen before you see the Apple icon at startup.
This problem can be caused by a faulty USB device or USB Hub. For example, some connected hard drives may result in the system hardware attempting to identify the drive, or possibly scan the drive to determine its configuration. Multi-function devices can be perceived as external drives of they have memory card readers.
Try unplugging all unnecessary USB devices, then startup the computer, and then connect the devices again. This may speed up the startup process.
Something else that may slow down the startup process are synchronization applications for services like Dropbox, Box, Google Drive, and Microsoft OneDrive. Try configuring these mini-apps to not load at startup. That will likely speed up the startup process. You may want to choose just one synchronization drive service.