Ack. I've seen this before. Cold boot takes forever, reset is normal. Every time I've seen this it's due a driver error caused by fastboot. When you windows shutdown a pc, everything in your ram gets shutdown. Ram is blank. If fastboot is enabled it saves all that info on C drive first, so when you hit power on a cold boot, all your drivers are immediately returned to the ram. It means not having to find and reload all the drivers from scratch, can be much faster boot. Reset is different, it's a total wipe of the drivers and a full blank start from scratch, no fastboot.
So, that said, when you are operating windows, at sometime it's loading a driver that's in conflict with another, but currently not used. During fastboot, that conflicting driver is loaded to ram, and bios uses/checks every driver, so you get loops. If you really dig through your bootlogs and windows event viewer, you can probably find the culprit driver, but mostly they'll be legacy drivers from audio or lan that are conflicting with what windows wants to use.
Best immediate fix is to disable fastboot. With an SSD as OS drive, it really doesn't hurt, your cold boot times will be identical to reset boot times.
http://www.sevenforums.com/tutorials/819-hibernate-enable-disable.html
Use option #1 in a admin window. Should fix the issue. You also might be able to revert to fastboot at a later time, after most drivers go through upgrades.
Oh, it's Windows 10. Just because you didn't update, or authorize any updates, doesn't mean it didn't get updated. Windows will automatically update itself for minor fixes, bug fixes, security updates etc and never tell you. It's really only major updates that require your permission, like build changes etc.