[Nanolettercase]

Hi everyone,
I have a query about impedance measurement, I hope you would help me with this.  It must be quite simple but I have almost no experience on the impedance
 measurements. 
The three electrodes system I employed, platinum working and counter electrodes and  Ag/AgCl reference electrodein 75％ H3PO4, connected to a standard potentiostat (it has fra).  I filled measurement condition as follow: "10kHz to 0.1Hz with 106 frequency.  Keep 0.5 V which is the rest potential."  I started collecting data then its very unstable at initial 10 data points in Ohm vs. Ohm plots.  Is it normal or lack of instrument's ability ?
How could I estimate the solution resistance with this?