This behaviour sounds like what would happen if you use the timer and have the shutter set to "B". When the timer counts down, it slowy drags the shutter button down, until it fires. Typically, if you have a faster shutter speed in normal operation, it will click and reset. If you have it on "B", the shutter will stay down for a second or so and then reset back to its normal position.
If you are after a manual, do a google search. www.butkus.org will have it available for download.