Been getting random BSOD for months

Hi, I bought a new computer a few months ago, it never worked properly and even after i sent it back to the shop multiple times it has never been properly fixed. The BSOD happen at random times, sometimes it will go two weeks without issues and other times it will crash 2 or 3 times in one night. I've looked through a few forums to try and find a solution but i've had no luck, i've given up...