It's probably due to some device initalizing slowly. Modern computers with SSD, if they boot so slowly, it's because they are waiting for some device and it's driver to complete.
Have you got fast startup on? By default it's on, and it wasn't available on W7. With it, every time you start the computer normally after normal shutdown, the system doesn't make a cold boot, but instead resumes the system part of Windows(kernel and drivers, excluding programs) from hibernated image. So if some device driver is faster to cold boot than to resume from such hybrid shutdown, it could be a cause.
If you restart the computer when it's on, does it then boot as fast as you'd like to? If yes, then probably the cause is drivers and the above, because when doing restart, it will make a cold boot. If not, then turning off fast startup is probably not going to help.
http://www.eightforums.com/tutorials/6320-fast-startup-turn-off-windows-8-a.html (some basic explonation of fast startup, introduced in W8)
Another thing, W10 might have a bigger swap since it's now mostly with default settings. I recall since Vista or at latest W7, by default Windows will scrub the swap file/s and hibernate file as they contain data from memory. If they are large enough, it might cause some delay even with SSD. You can turn off hibernate option and delete the file, and set temporarely a small swap file. I vaguely remember the files might be swept when shutting down, but they can also be swept when starting.
Windows has performance monitoring capabilities than can be used to figure out what phase in startup is taking how much time. I've been using XP for long which didnt't have that stuff, so here's just a link for some details about the system. I think it's found in the same place as in W8.
https://www.winhelp.us/troubleshoot-performance-in-windows-vista-and-7.html
It will take some time to look through but should be pretty straightforward. On my computer typical causes for increased boot time are caused mostly by Search Indexer and that antivirus thing.(on Windows GUI it's Windows Defender but in logs it's referred Antimalware Service) And this performance feature writing the logs automatically compares the executing time of each phase or device, againts the average time of that, on each computer.
I'm not using the fast startup as my computer takes many minutes to boot anyway due to post memory test, I don't know if with fast startup, is there is similiar log, because with it, the system should resume by just reading the whole kernel with drivers from disk. It might have something? Because when I do full hibernate like I did just now, there is nothing on the logs about how long it took to resume from hibernate.
But like I said about, it might be some driver does not like being resumed so that will take longer or maybe the driver stalls and crashes, and is restarted. Some external devices are known to be difficult with regular hibernate too.