Macbook Pro mid-2010 used for work and kept in good condition. Intermittently has trouble turning on. When that happens, it needs to be left on the charger for a while before it will turn on. You can hear a faint rhythmic whirring sound as it's trying to turn on. It takes a few hours but does turn back on eventually. There may be a part that needs to be replaced but I haven't taken it in to be diagnosed by Apple. My workaround has simply been not to turn it off. Computer functions fine once it's on.