The first cause of the laptop being slow to open up programs is that there is not enough RAM. If your computer crashes or struggles to load basic programs, you may have a problem with your RAM and need to upgrade/replace the RAM. A second cause would be a hard drive error. This may be caused by incorrect shut-down procedures. The first step is to restore the original windows operating system. If that does not work, your hard drive most likely has hardware problems and needs to be replaced. Samsung NP-R580-JBB2 Troubleshooting

A cause of the laptop shutting off without warning could be due to the laptop overheating. A buildup of dust can cause a computer to overheat. Using a compressed air duster, carefully blow dirt and dust free from the fan and vents. The heat source could also be caused by an accumulation of dust in other areas of the laptop such as the hard drive and RAM. Try dusting these areas with the compressed air duster. Samsung NP-R580-JBB2 Troubleshooting

A possible answer is that the either the battery or adapter is faulty. Check to make sure that the AC power adapter is plugged into the DC-in jack on the left side of the laptop. If it is plugged in to the laptop, make sure that the light on the adapter is on (there should be either a red or green light showing) and that the adapter is plugged into the wall outlet. If the light is on and the adapter is plugged in to both the laptop and the power outlet but there is still either no power or the laptop does not show that it is charging, then the battery at the back of the laptop is faulty. However, if the adapter light is not on, then the adapter is faulty. Samsung NP-R580-JBB2 Troubleshooting