Sometimes the internal components of a PC require attention to continue functioning properly.  The issue can be as simple as re-installing a component driver (software that allows your computer to communicate with hardware or devices) or they may need a firmware update. But computer components can simply wear out after long periods of heavy usage.

Hard disk drives are constantly spinning while a computer is running so read/write errors can occur; RAM memory module pins can become damaged; internal cooling fans can fail; laptop DC input jacks can break.