Here are some of the things that you should look for or diagnosis..
1. Switch power connect from video card with another and also pull the 20/24 pin from main board(Most likely these or otherwise it's Nvidia's Driver)
2. check temperature of all hardware
3. Reset OC
#2 was what happened to me yesterday, turned on game and restart and i did this like 3 times and BSOD on them, I switch the GPU's power connector and it seems fine so far, haven't have any BSOD ever since then...