Q: Involuntary restart

Hey guys,

I have a Macbook Pro Retina, mid 2012 and recently my Macbook started restarting involuntarily every 4 days or so and when I start it it takes for about a minute or so before the display reacts and I get to the login any hints on what to do or what might be the problem in the first place? It is not a matter of the display the computer does not react for about  minute.

Thanks in advance!