Hi Ange. No, it isn't normal, neither is having to to re-install your OS every year!
Your OS should access your HDD at the same speed whether it's virgin, half full or full. What will slow access times is "what" it's accessing EG: large/complicated programs/files.
This slowing down manifests also at boot up and close down.
Put simply, more work it has to do, slower it becomes. It really is that simple.
Your specs seem OK, the HDD is in good shape with regard to fragmentation, so I would look at just what is being run and closed each time you switch on/off. You may have programs with their own running "engines" which are notorious for slowing PC's. I refer to real time scanners for AV, Malware etc, so also have a look at just what is running in the background.
You may already run CCleaner? If not, google it and run it. It really does get rid of the rubbish especially from the registry (always back up registry clearouts). Another tip with CCleaner - by default it is set to empty your waste bin. You may not wish this so deselect it.
The only other thing I can think of is to closely monitor everything you install after your OS and try to see just what impairs the performance.