Laptop won't start after restart

I have an Asus K50IN laptop, which I recently took apart to clean it from dust, during that I screwed apart the cooling system, hard drive, SD card reader chip and CD/DVD-player device. (And I just took them apart from the PC, not individually apart, so that I could just be able to reach more places inside laptop's interior.) Then I put everything back the way they were, and also applied new thermalpaste to CPU and GPU. When I turn the PC on, it goes OK, works all the way 100%, but when I restart it, it boots 'til the Asus logo, but then suddenly shuts down, when I start it up again from Power switch, it also dies at almost the same spot, and this process continues as long as I restart it right after previuous crash. Now the interesting part is that when I let my laptop rest for a couple of minutes for example, or even couple of tenths seconds, it starts OK, and everything works. But as soon as I want to restart, this scenario happens again.
I have freshly formated Windows 7 which worked just fine, but then I took it apart, and this restart-startup problem occoured. And when it wants to shutdown then it will, it doesn't matter if I reach BIOS menu, or boot menu, with F2, F12 keys on my pc. I have done startup repair but no use.
Any help would be appreciated!

Hello Mcarno;

It would seem to me that you didn't get everything back 'exactly' as it was prior to you opening the case and doing the work you mention.

But I'm having a hard time figuring out what the problem might be. The 'rest for a couple minutes (or even couple of tenths seconds), it starts OK' thing kind of suggests it's power related? But that's just a wild guess and I can't think of anything that would cause that.