Your PC is on the floor?
Then chances are when you bend down to open it, your head is lower relative to the body than usual. Blood rushing to the head or something can cause headaches. Possible cause.
Also the possibility you'v just been sitting too long, blood has pooled in the lower parts of your body and if you get up (or down) too quickly it results in a massive loss of blood pressure, causing dizziness, fatigue and your vision go white in some cases. Its called Orthostatic Hypotension.
Or maybe some kind of Placebo Effect, your mind thinks that is what will happen so it does that.
Basically, the computer is not sending out harmful waves. Chances are much more likely that its some oddity of the body