Was jumpseating the other day when the A/P disconnected in climb out due to intermittent SPD LIMIT FLAG. The PF was obviously caught off gaurd, hands all over the MCP.. LVL CHG.. nothing happens, dials in low V/S. Speed is slowly decaying towards up speed and I can't help but finally saying from where I am sat "the autopilot is off".. as you might have guessed A/P disconnect horn kept singing throughout the rather messy recovery. At the end of the flight the A/P finally came out at 500 ft fully configured on a beautiful SKC day destination.