Nothing new has been installed recently ? If so, remove the application and test.
blue screen and freezing : during a reboot or sunddenly ? Is you MBP noisy (dirty fans ..) ?
My advices :
1st : SAVE YOUR DATAS in emergency : burn your homedirectories or copy them into an external USB drive
2nd : if you do not know anything on maintenance, give it to a specialist to be deeply checked