|Have you, or is it possible someone else who had access to this computer...|
- dropped it, or dropped anything on it, or otherwise exposed it to a physical jolt ?
- spilled liquid on it, or sprayed it with liquid, or exposed it to liquid such as rain ?
Since the computer last worked properly all the time, has there been a power failure event that happened while the AC adapter was plugged in ?
Those things are the most frequent reasons something inside the laptop has been damaged.
Your laser lens may be "dirty" .
Eject the tray, with no disk on the tray clean off the obvious laser lens with a tissue or a soft cloth.
If that doesn'r help....
Dell™ Inspiron™ N4010 Service Manual
Try unplugging it, plugging it back in.