Actually, to me, this sounds very much a video card issue, if your monitor isn't detecting the video card at boot-up, that seems like a video card issue. Or, some part of your computer may be overheating. Personally, to start off, I would recommend the program CoreTemp to see if your overheating. Once you download the .zip, just run the .exe file, or extract then run, for future ease of use. You will see numbers on the bottom-right of your screen reading in Celsius.