Had similar problem with my Steelcase chair: every time I'd stand up and my heels touched or came close to metalic part of the chair there was an electrostatic discharge that causes the screen to flicker on/off for a moment. My previous chair never had the problem.

Solved by an anti-static floor mat from Floortex. Interestingly only one of the screens reacted this way, the one connected through displayport, HDMI seems more forgiving of electrostatic interferences like this.