Hi
You may also like to have a look to these papers

L.Castañer S.D.Senturia ‘Speed-energy optimization of electrostatic
actuators
based on pull-in’ IEEE Jour. of Microelectromechanical systems (JMEMS) ,
Volume
8, No. 3, pp 290-298, Sept 1999
L. Castañer, A. Rodríguez, J. Pons and S.D. Senturia ‘Pull-in
time-energy
product of electrostatic actuators: comparison of experiments with
simulation’
Sensors and Actuators :Physical A, Vol 83/1-3, pp. 264-270, May 2000
L. Castañer, J. Pons, R. Nadal-Guardia, A. Rodríguez ‘Analysis
of the extended
operation range of electrostatic actuators by current-pulse drive’ Sensors
and
Actuators :Physical A,vol 90,nº3 ,pp 181-190,  May 2001
J.Pons A.Rodriguez and L.Castañer ,’ Voltage and pull-in time in
current drive
of electrostatic actuators’ J. Microelectromech. Sys., (JMEMS) vol. 11,
nº3,
pp. 196-205, June, 2002
R. Nadal-Guardia, A. Dehé, R. Aigner, L. Castañer, ‘ Current
Drive Methods to
Extend the Range of Travel of Electrostatic Microactuators Beyond  Pull-
In’ J.
Microelectromech. Sys. (JMEMS), June 2002, pp.255-263


and related refeences which describe charge mode driving. One of the simplest
thing to do may be to add a series resistor in series with the
drive voltage source to reduce the charge spike arising at the pull-in
(see the first of the above papers)

Luis