Windows doesn't ever do a disk check for a drive without errors (unless the flag isn't being reset - but then again - that's due to errors.) Since it is checking, you can assume that there is something wrong.
If power is immediately cut from the system without using the power button or Windows shutdown (like if power fails without UPS or plug is pulled) then that could cause a disk check.
"I have found that, if you attempt to cancel during the 10 second countdown, it will always hang; however, if you do not press any key, sometimes it will complete successfully (perhaps 1 out of 5 times?)."
This statement of yours almost is guaranteed to = failing HDD. Nothing else would really cause that.