So I’m just going to throw this up on here, do with the info what you like.
My previous workstation had the same issue; heck even at work I see the same issue.
I recently built a new workstation (I do so every 2-5 years) and this time I wanted to future proof as much as I could, for as long as I could; for the first time ever I cared more about performance than budget.
Know what was a game changer?
This: http://www.newegg.com/Product/Product.aspx?Item=N82E16820147467
Get one of those- all your “wait” problems go away.
Windows 7 Pro: starts up instantly and rdy to go (background services, startup apps, etc. all load so fast, to you it feels like Win started instantly from a cold boot)
DCC apps (Maya, ZBrush, Photoshop, etc.): start up in about 2 secs
UE4 (depending on the project): starts up/opens maps in anywhere from 2 secs to about ~30 secs for really heavy projects
You’re problem is hardware related, not UE4. Get a faster HDD and you’ll work more efficiently.