Howdy. I had a similar problem, but not sure if the same. My computer would start into Windows with no display sometimes, just like you, and when I restarted it was fine. Later on, it would sometimes start to a blinking gray screen-- unclear if Windows was actually starting up or not. Once again restarting made it work normally. Around the time the gray screen symptom began, new games started running terribly. It was only when I went back to older games and saw poor (though not as poor as new games) performance, that I thought something had gone wrong with a component in the computer. I checked all wired and motherboard connections, and then a friend with more PC hardware experience said it was likely bad RAM. I replaced the RAM (as well as upgraded it) and have not had this problem since.
I would take a shot in the dark, at least reseating your RAM if not buying replacement (there's usually room for more RAM!)
A few questions:
When the display is not working, does your computer seem to have booted into Windows successfully (do you get any startup audio etc)?
Have you noticed any performance issues in game that started around the same time as the display issue?
Have you ever had any other strange displays on boot, like a flashing gray screen?
Please list further hardware specs such as RAM if possible.
