When i turn it on it says turn off and on again

I have just had exactly the same thing on my daughter's NV3. In this case the lens cover would not open but if you power on the camera with you finger on the display button you can view stored images. If the lens cover is jammed you need to open the casing and maybe take the lens cover assembly apart. You need a very small cross head screwdriver (No.00 should be OK). There are 5 screws in total, 4 screws on the outside of the case (3 plus1 under the headphone socket cap) and 1 inside the battery compartment. You need to remove all 5 to remove the camera front casing. There are some retaining springs top and bottom on the front cover, gently prize off to reveal the lens cover assembly. Check to see if the lens cover will operate by switching on and off - if it works then the camera front casing is preventing it from opening and is probably bent out of shape. A little careful bending back into shape should resolve the problem. If it still does not work with the casing removed, read on. This is the tricky part. There are two extremely small, black retaining screws to the left hand side which hold the assembly onto the lens cover motor. Remove these screws and the front of the lens cover assembly to reveal the lens cover and the back plate of the assembly. Lift off the lens cover and switch on the camera. If the motor is still working, you will see a short black peg move from side to side as you turn the camera on and off. Thoroughly clean the lens cover and assembly, remove any obstruction and replace the lens cover making sure you locate the hole in the lens cover over the motor peg (described above).
The motor is magnetic and will attract the screws away from their holes if you replace the assembly front straight away, so when you replace the front of the lens cover assembly, place the screws in the correct holes before lowering it into place and then screw onto the motor/assembly back. Test that the lens cover opens and closes and replace the Camera front cover taking care not to bend it too much - if this becomes distorted it can stop the lens cover from operating resulting in the same problem.