Random Parking Brake Engagement

I very rarely use a parking brake, unless I park where it's not level. My garage is level, where I park at work is perfectly level. The parking brake on this x15 seems to engage itself at random times for no apparent reason. It is very irritating to put my foot on the brake and start the engine, leave my foot on the brake while I put it in gear and take my foot off the brake and expect to go, and nothing happens. Then I have to look at the instruments to see that the parking brake is engaged. Then I have to put my foot back on the brake to disengage it. I did not engage it. Does anybody know why this thing apparently engages on it's own at random?