I can confirm this behaviour, but it is (usually) not a problem and has a pretty normal reason.
Does this also happen with other software and files from the HDD/network?
Did it happen before, like it was always this way, or just recently? If so, what did you change?
Will the 100% CPU usage remain or sink after the file is completely loaded?
"After (opening) 5-6 documents" means opened "all at once" or "subsequent"? If all at once, how much RAM do you have and is there enough space left on the HDD for cache?
Is preflight activated?
Do the documents have broken cross-refs to other documents?
What means "hanging"? Hanging like "for a while" or like "forever"?