...or possibly the power supply isn't correctly connected. If you constantly need to reseat the card, then the shifting of the card is wiggling something on the board which causes a "good" connection to take place.. So, you might start by completely reseating the motherboard so all setoffs are right.. Make sure all power connections and cables are reseated.. Things like that.. If the computer still doesn't work, try replacing the powers supply.. And if still no joy, I'd replace the motherboard.
Hope this helps.
At the far beginning, I try to connect my computer with two screens, it works for a while, then one screen's signal got chaos, then I only use one LCD monitor for a while, sometime when I try to boot up the computer, no video signal, no keyboard signal and mouse is not light up. Then I changed my video card to a new one, work for about a month, same problem happened. everytime I boot up, it failed. then I figure out a temporary solution, reseat the video card, it solve the problem everytime. But it is quite inconvenience. then I find a easy way, before I boot up computer every morning, unplug the power line, give a little small movement on the video card from outside(just little touch), then connect the power, the computer boot up every well. However this doesn't work all the time, this morning it failed, I still need to open the computer, reseating the video card to boot up the computer. Anyone can help me to figure out what the real problem of this? Thanks.