If it is a hardware issue, it can happen anytime. When was the last time you used a can of air to blow the dust out of the machine? If you never have, do the following:
1. Go to your nearest electronics/computer store.
2. Buy a can of compressed air.
3. Shut down and turn off your computer.
4. Unplug your computer from the wall and then remove the battery.
5. Take the can of compressed air (making sure it remains upright the whole time) and blow into any vents on the computer to flush dust out.
6. Put the battery back in the computer and plug the computer back into the wall.
7. Turn your computer on and see how it runs.
Before you get a can of compressed air, do the following steps to see if it may be an issue with the BIOS:
Note: backup any files if you are using a RAID controller of any kind.
1. Go into your BIOS and load default settings to clear the CMOS memory.
2. Save Settings and exit the BIOS.
3. Shut down and turn off the computer.
4. Unplug the computer from the wall or surge protector (then remove the battery if it is a laptop).
5. Hold down the power button for 30 seconds to clear the software connections between the BIOS and hardware and clear any corruption in the temporary memory.
6. (If it is a laptop, plug the battery back into the laptop and then) Plug the computer back into the wall.
7. Turn it on to reinitialize the software connections between the BIOS and hardware, and post back how it runs.