An electric dipole of dipole moment p and moment of inertia I is placed in an uniform electric field E. it displaced by some angle θ and released, then

Frequency of dipole is inversely proportional to $square root of moment of inertia$ 

Time period of oscillation does not depends on mass of dipole

Dipole undergoes SHM if θ is small, releasing oscillation energy into heat and acquires stable equilibrium   position

Dipole soon acquires its stable equilibrium position