A person who is subjected to Hold Person, presuming they fail their save, is paralyzed. This means they can only take purely mental actions. Furthermore, the target of Hold Person must be humanoid.
As far as I am aware, Wildshaping is a purely mental action. Though I am not actually certain if this is the case. Would it be possible to wildshape into an animal while under the effect of Hold Person? And if yes, would the fact that you are no longer a suitable target mean that the spell is supressed- Even though it has already affected you?