On Windows 8.1,
Have some app on your desktop, say TestApp. Make a shortcut.
Windows+R, type "shell:Common Startup",
Drag that shortcut in to the "Start-up" area you now see.
(NOTE: if you now go to Task Manager, and select at the top the 4th tab, "Start-up", you will in fact see TestApp listed and "enabled".)
Restart the machine.
AFTER Windows 8.1 starts normally, everything,
IT WILL WAIT about 10..12 seconds, and THEN correctly start your TestApp.
This has nothing to do with machine performance, it always waits the same time.
It has nothing to do with the app in question (perhaps, the app uses networking, or similar woes) .. you can try any simple or complex app.
It has nothing to do with Windows "doing other stuff". You can carefully remove any other crap that may be on your machine, and it will still do it.
Does any genius know how the heck to reduce or eliinate this unusual seemingly built-in feature of a 12-15 second pause, before Windows starts start up items you have added, such as TestApp in the example given? Thanks in advance - it is very difficult to google this as 1000 other related issues appear, have not been able to find a fix anywhere.