I researched the Canon site and the E18 message relates to a lens issue. Your lens sounds like it's "jammed" and so the camera is displaying the error message. According to the Canon online support, the error is temporary and should go away the next time you properly turn on the camera. Howevcer, since you say it happens every time, it may be a bigger issue with the lens. There suggestion is to have it inspected by a certified repair person.
This is what I got off the Canon site:
Issue: Lens will not move and camera may display an E18 or "Lens" error.
Solution: Possible solutions for an E18 or Lens Error message PowerShot A410
The "E18" or "Lens" error message indicates an error that involves the lens unit or lens cover.
This error may appear where the lens is prevented from properly extending or retracting such as, for example, when pressure is applied to the lens or the area surrounding the lens while handling the camera. The error may also be displayed if the lens unit/camera has been subjected to an external shock, or if a foreign substance (i.e. liquid, sand, dirt) enters the camera.
Check the following when you operate the camera to avoid applying pressure to the lens and surrounding area:
* Hold the camera so that your fingers do not touch the lens unit when you are shooting.
* Make sure the camera is off before the camera is placed back in the case. Exercise caution to ensure that the camera does not accidentally power on while the camera is stored inside the case.
If you cannot clear the error code by turning the camera off and then on again, or if the error code is displayed frequently, a camera malfunction may have occurred.