When the hinge line is ahead of the control surface's center of mass, there is a positive feedback loop. The wing acceleration caused by the control surface deflection acts on the control surface's center of mass to increase the control surface's deflection until the wing has deflected enough to resist the force and then, just like a penulum, returns which causes the control surface to reinforce the motion in the other direction. This oscillation continues until something breaks.
Full scale aircraft usually have control surface counterweights called "mass balancers" that are adjusted so that the control surface's center of mass is on the hingeline. The importance of this mass balance is one reason that even something as simple as a paint job needs to be done by a certified A&P on full scale planes.
Mass balance can be used in models also.
At high enough speeds, even wings without control surfaces can flutter, i.e. a Gentle Lady glider in a long steep dive. Even propeller blades have been known to do it in high rpm pylon racing engines. The prevention of flutter is why a lot of helicopter blades have lead wire glued in the leading edge.

Make the control surfaces as light as possible.
The linkage should be as stiff as possible.
Consider the inclusion of control surface counterweights on high speed models.