When a Windows computer starts up, it will start any programs or services which are configured to launch at startup, in addition to loading the operating system. Some of these may not be necessary and disabling their launch could speed things up a bit. A useful tool for looking at the startup configuration is Autoruns. You may not know when you review the list if a particular program or service is necessary but you could post a new question or follow-up comment to ask for more information about the effect of disabling one.
But my suggestion for your issue would be to consider using two features of Windows which work very well and which can easily speed your startup time - Sleep and Hibernate - rather than shutting down your computer as often.
Most computers will wake from Sleep almost instantly. One possible disadvantage is that the computer will use a small amount of power even when it is sleeping. If you use Hibernate, it will take a little longer to resume (but not as long as from a cold boot) but one advantage is that the computer will not use any power while it is hibernating.