Windows 7: Auto shut off/Computer won't turn on until several tries later

*Disclaimer - I'm not sure if my post is windows 7 related or even in the right category, I just had to post my experience to try to help others with the same problem. I tried researching this problem and was unable to find the right help or solution. It might be an easy fix for you guru's so don't flame an average guy trying to share his experience with others. Thanks.

This "crash" on my recent computer has been bothering me on and off for the past 6 months. I recently decided to do something about it by taking to local shop of where I get my computer stuff done. The computer in which this is happening to is a desktop, custom built for business/entertainment. Nothing high end for gaming or video editing etc. The desktop is current running windows 7 and nothing fancy about it.

So about 6 months ago I would noticed that my computer would not turn on when I pressed the power button. The "on" indicator light would flash when I pressed the "on" switch and I could hear the sound of my computer turn on but would quickly shutoff in less than 2 seconds. I would press it again and it would be the same, sometimes is would take one try and the computer would turn on, sometimes is would take 7-8 times before the computer would turn on. This experience reminded my of an old car that would take several cranks to turn on.

In addition to this problem, I noticed that when I would stream two or more live sporting events online that my computer would completely shut off. When I turned it on again, DOS did not have that error screen of saying how the computer was not properly shut down and would bring me straight to windows like nothing happened.

With the "turning on" problem I could not pinpoint any patterns of when it would happen. It could be night, could be day. Could be after serveral days of not using it and it could be right after a long session of using the computer. The auto shut down of watching two streaming videos also came and went as it pleased. Sometimes I would just be browsing the internet and the computer would just turn off on it's own. (No I don't have a ghost in my house nor do I have any viruses on my computer).

So after leaving my desktop at the computer store for over a week, the guy tells me nothing is wrong with my computer. Says he's been playing with it all week streaming videos, turning it on and off, and even installing a program to help monitor the computers internals (sandralite?). Charges me $65 for not doing anything and telling me that my computer is fine when it's not.

Finally I bring it home and turn it on right away to prove to him that he is wrong and it works. Turns on right away like it suppose to and Im streaming two videos at a time and not shut off. Wow? What did he do? I thought to myself. 3 days later, the computer doesn't turn on and back to the multiple cranks. So I started unplugging all my usb ports and played around with it and it turns out that my logitech wireless mouse and keyboard might be the reason why this is happening. During a string of cranks of turning on/off my computer, I noticed that everytime I unplug my usb for my wireless mouse/keyboard my computer would turn on right after. I am still not sure if that is the solution but for the last 5 days it has worked. I also updated the driver for the keyboard/mouse to see if that will help so I don't have to unplug my usb before I turn it on everytime.

Any others with the same problem or am I just that lucky?