I had this problem a week ago on a vacation using my 1st beginner's DSLR ,a Nikon D40.
If its under Nikon Warantee,you can turn in to the dealer & wait for the repair but what if its beyond warantee period, or you bought it used with expired Warantee?
Here's my solution to fix it to save some repair charges and guess it might bless someone with the same problem there.
There is a gear motor that controls the tripping of the Shutter Release mechanism and over time,it either gets a bit tight to turn over or just contaminated with dust & needed soe light lubrication to get it back to normal( provided the motor is still ok).
Step 1: Tools & Stuffs You Need
Small Watch Maker's Phillips Screw Driver
Can of Spray Grease (or any General Purpose Light duty Grease)
A Clean Dust free Environment
Step 2: First, Remove Its Battery.
You can recharge it if its is low for testing later.
Step 3: Remove the Bottom Base Cover Plate
This will expose the Gear motor operating the shutter which neede to be serviced .
Step 4: Removed All Screw Holding the Base Cover
Step 5: Proceed Removing All Screws in a Sysmetic Clockwise Order
Step 6: Remove All Screws and Aside It on a Piece of Tissue Paper
Step 7: View of the D40 DSLR Base With Cover Removed.
Step 8: The Gear Operating the Shutter
Step 9: Lightly Move the Gear & Inspect for Contamination
Stop here & move Downwards while inspecting for contamination & smoothness.
Step 10: A Closer View of the Gear Seen Through a Magnifying Glass
Remove any visible contamination trapped between teeth of Gear .
It should give a smooth feeling when lightly pushed until it stops.Don not push beyond but reverse in opposite direction.
Step 11: Repeat About 5 Cycles.
Step 12: Apply New Grease Between Gears
I use a Can Spray Can and is able to have good control on the amount dispensed.
Practice first on other area if you are new to using a spray type Grease as you do not want to smear all over causing more harm than good.
Step 13: Spray a Little at a Time & Move Th Gears
Step 14: Move the Gears 5 Cycles to Spread Out Grease
Step 15: Insert Battery & Test Before Closing Up Cover.
I made a few shots on Program mode looking at Gears turning each time the shutter opens & closes!
Made it! firstname.lastname@example.org
Step 16: Close Back Base Cover & Have Fun!
Put back the base Cover & Screws starting from the Inside of the Battery compartment,
Work in an anti clockwise direction noting the length of Screws (long ones at battery compartment & lens mount)
Tighten lightly using 2 Finger force until all are in place.
Retighten with only finger force in opposite direction.
Put in the Battery,close the latch ,turn on power & Have Fun Shooting again!
A blessing from Jitra,Malaysia to all.
From the desk:
Designer of Tims Waterfuel, 20C,Taman Bahagia,0600,Jitra,Kedah,Malaysia.