Q: Macbook mid 2012 emergency restart/shutdown

Hello, i have a macbook pro mid 2012.

Overtime when i am on my macbook browsing the internet with safari my macbook suddenly freezes and restarts.

it says it's an emergency restart and i send the report to apple. Only thing i am doing on my macbook is watching a stream on twitch, searching things on google, browsing stuff on amazon and calling a friend on Skype.

How can this emergency happen???

I did replace the thermal paste on my processor with Arctic X2 but i don't think thats the problem

These are my specs:

Macbook pro 13 inch mid 2012

intel core i5 2.5ghz

8gb ddr3 1600 mhz corsair vengeance (upgraded myself)

500gb samsung evo 850 ssd (replaced with original HD)

Intel HD graphics 4000 1024mb