Sony Vaio refuses to turn on for no reason

I have had a Sony Vaio notebook, for about 3 years.  Recently, it just refuses to turn on for no reason at all.  I mean, the power button does not work, and nothing starts.  Just when I was about to give up (3 months later) and tried one last time on the power button, it turned back on!  After a couple of months of working fine, it died again.  A couple of months later, it came back alive again! I did absolutely nothing to it.  It never dies when I am using it – only when the laptop is shut off, and the next time I try to turn it on, it does not respond.  The only clue that I have is that windows takes a long time to load (but that may just be the many programs I have installed on it).  I tried cleaning the fan, but no use. The battery is not the greatest, but it does not run even with the battery removed. It does not seem to be overheated because the processor does not even get any power to it.  After 2 repair shops, nobody seem to be able to tell me what the problem is.  I would greatly appreciate it if you could help! Thanks!

It’s very hard to troubleshoot a laptop with a problem like yours. An intermittent problem is the worst!
I would recommend unplugging the battery, wait for couple minutes and then try to start the laptop using just AC power, but it looks like you’ve already tried it. I had a Sony laptop before and got the same problem 2 times. I was able to get my laptop back to live by removing the battery and starting it from the AC adapter.

I think it’s possible you’re your AC adapter might have an intermittent problem.

It also might be a loose connection somewhere on the system board. If I would get this laptop for repair, I would open it up and reseat all connections on the motherboard. I would try to strip it down to minimize the system and leave just the system board, the memory and the CPU and try to turn it on with an external monitor attached. If the system still doesn’t work even when it’s stripped down, I would suspect that the motherboard is bad. I know that’s not a lot of help, but that’s what I would try to do.