I would suggest opening CCleaner and unchecking the "Run CCleaner when the computer starts" box, which is located under Options > Settings. This may solve your problem.
Also, if you do have to reboot your computer, waiting 30 seconds before you restart wouldn't make any difference. In fact, you are actually better off rebooting it immediately after shutting it down. The reason being, waiting 30 seconds will cool your computer slightly, and restarting afterwards will heat it up again, which cause abrupt expansion/contraction of your components, which eventually wears your computer down faster. If you boot it immediately after shutting it down, your computer's temperature will not substantially drop, so it will last longer.