If your Mac is feeling sluggish when booting or starting up it’s probably a result of a few things: a bloated login item list, too many windows being restored, a super slow external drive that takes forever to be accessed, or even just the general hard disk speed. The good news is that most of these are very quick to fix, so follow along and you’ll be starting up a Mac quicker in no time at all.
1) Clear Out Login ItemsRemoving unnecessary Login Items can make a significant difference in boot time simply because there are less actions for the Mac to complete before the computer is ready to use. Login Items can be helper daemons, menu bar items, or full blown apps, get rid of anything you don’t need to automatically start or that you don’t use often.
Read the entire article here: 4 Tips to Speed Up Reboot & Start Up Time in Mac OS X.