I have exactly this problem on a satellite s50 and it also coincided exactly with the last windows update (creators fall edition)!
However, my experience is slightly different in that after powering up I would see only a black screen (looks to be off, with no cursor), but eventually I would see the login screen (average of about 1.5-2 hours). Once up, the computer ran fine and just as well as pre-update, and there were no issues resuming from sleep.
I tried changing startup options (clean/safe boots weren't much faster), updated drivers (cant access BIOS menu but they look up to date), tried repairing Windows/the Windows update (no joy), but problem persisted. So was also thinking it may be a hardware thing... perhaps a GPU issue or possibly failed SSD drive (although my HDD has plenty of free space). Decided to use last software option of rolling back to previous version of Windows in recovery options (as it was booting in seconds before the update)... Computer has now been on black screen for over 24 hours!
Question is what is best course of action now? Should I just force shutdown even though it may be doing something, or is it likely in an 'infinite loop'? Difficult to know for sure as cannot see anything on screen.
I have all data I need backed up and have a recovery install on usb, but I can't access the BIOS or any other boot menu so running out of options... anyone have any ideas?