Windows 7 Random restarts but no BSoD

[Aastalel]

I just installed a new graphics card and a new power supply... Now I get these random restarts. When I come back, I'm notified rhat Windows has recovered from an unexpected shut down.

Really frustrated at this point. What could this be?

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[GeneralHiningII]

Press Start.
Right-click "My Computer" and select "Properties".
Select "Advanced Settings" and then "Startup and Recovery".
Uncheck the box "Automatically restart".

Then try to recreate the problem.
List all the events that you've done before the crash.