This is actually a usual error. The occurrence for this problem is with the lens extension mechanism that automatically gets activated when camera is switched ON. This problem can occur due to dirt available in the camera or other grit creating problem in the camera mechanism.
Other possible reasons could be physical issues during operation or low battery during the operation.
Solutions: So, to fix the above mentioned "lens error/restart camera" error, follow the below mentioned fixes:
1st Solution - The first thing that you should do is to remove the batteries and memory card from the camera. After 1-2 minutes put the batteries back again and make sure it is charged enough and then insert the memory card.
Next, switch ON the camera and check if problem still persist or not. If it still persists then follow next solution.
2nd Solution – Blow the compressed air around the lens mechanism with the help of hair dryer but with no heat setting. Also you can slide a piece of paper around the lens area in order to remove any kind of dirt or grit that might stuck in there.
3rd Solution – If none of the above solutions work for you then, you must send your camera to service center.
For other common camera errors and solutions, check out: http://www.rescuedigitalmedia.com/7-common-digital-camera-errors-their-solutions