Your processor is like the brains of your computer it does the calculations.
It”s common for processors to use a large amount of processing power for short periods of time when loading software. That is why the more programs you have programmed to load on start-up, the longer it takes to start up .
Scenario
You have six programs that load at start up, and all require 6 seconds loading time. That is roughly 30 seconds longer than if you had only one program loading at start-up. Generally as a computer gets older the owner will install more programs . Many of these load on start-up because software makers often program their software to load during start-up to try and make people use their software more.