Although the problem is quite common, after googling for several hours I didn't find an appropriate solution for my particular case.
I got a 2011 MacBook pro with the latest OS (El Capitan) and it has the following problems.
- After several minutes of inactivity it hibernates and eventually I can't turn it back on. It only shows a black display and doesn't respond to any action. Thanks to the power button I can only turn it off.
- Turning on the mac requires me 20 minutes of trial and error. I have to try almost 15 times to boot it. It gets stuck on a progress bar screen which doesn't go further than 50%. Sometimes the progress bar is gone and a white blank screen appears. I have tried to boot with safe mode and the same thing happens.
I am worried that this can be a hardware problem. If that's not the case how can I "cure" this strange behaviour.