How long does your computer stay on for before it shuts down? Does it seem to be warm on the bottom of the computer? Does it start right back up? These types of things are usually due to overheating.
Used compressed air to clean out the vents on the computer. Keep in mind there are many vents on the sides, rear, and bottom of the laptop.
If simply cleaning the vents doesn't work, the next thing is to disassemble the computer and replace the CPU and GPU thermal paste. When the paste gets old it will disintegrate and crumble.
If you think it might just be software related, instead of taking the laptop apart, try re-installing the operating system using the recovery disks that came with your dell computer. If you don't have those disks, order a set from
recovery-disks.com to re-install the operating system and the drivers and utilities. We use recovery disks to get that done and its a really easy process.
Use
http
/www.recovery-disks.com/customcomputer.html this link to place the order for your set to wipe everything back to normal. This will rule out the issue if it is software related. If you continue having the issue once you re-install everything, then you can take it apart and clean it out using the above methods.