citroen c5 - steering - moo6570

I recently bought a c5 2.2 hdi 02 i find when driving on rutted surfaces on some roads the steering seems to have a mind of its own . Is this a common problem ?

citroen c5 - steering - Fernando P

I wonder what "a mind of its own " means?

citroen c5 - steering - Peter.N.

Could be down to the tyres, how much tread do they have, are the pressures correct?