Quick answer: Cloth.solverFrequency = 240. Iterations = 4. Sleep Threshold 0.5. World Velocity Scale 0.5.

Cape on character oscillates rapidly when standing still. Solver too few iterations.

The Fix

Cloth component:
  Solver Frequency:           240
  Solver Iterations:          4
  Stiffness Frequency:        100
  Sleep Threshold:            0.5
  World Velocity Scale:       0.5
  World Acceleration Scale:   0.5
  Damping:                    0.1

More solver iterations stabilize. Higher sleep threshold parks idle cloth. Lower world scale reduces over-reaction to character motion.

Verifying

Standing: cloth at rest. Moving: dynamic but not jittery.

“More iterations. Sleep aggressive. Calm.”

Related Issues

For ArticulationBody, see drive. For Rigidbody jitter mobile, see jitter mobile.

More iterations. Calm cloth.