I have a Toshiba Satellite L50-B-2G9, which takes hours to boot.
Initially I had Windows 8.1 and Ubuntu 15.10 installed side-by-side and switched between them regularly. I noticed it took longer and longer to boot. To rule out software I formatted the harddisk and did a clean install of Ubuntu 15.10.
At this point turning on the computer yields a lit up power button, a WiFi enabled indicator light (which can be turned off by the F12 key), a black (turned off) screen, a spinning fan and a processor which appears to be doing something as it is producing heat. I don't know if the hard disk does something because it's a solid state. After many hours, for the last couple of times I left it overnight, the laptop will usually boot and the OS will load. Once started all seems to be fine until the next reboot.
I'm guessing there is something wrong with the UEFI but I don't know how to troubleshoot this issue.
To rule out the disk completely I've also tried a live Ubuntu 15.10 but the results are the same.
As I mentioned the screen is completely off and it takes hours until the Toshiba startup screen shows. Once it shows, the computer works normally. To clarify the image below shows the screen I am talking about.
As requested, below is the SMART data. The disk seems to be fine.