Suffixes of this type indicate that the action described by the verb involves a change of some kind from the state of affairs that existed before the action took place.
-choH change in state, change in direction
maDo'choH we are becoming lucky, we are undergoing a turn of luck (Do' be lucky)
ghoSchoH he/she is beginning to go (somewhere) (ghoS go)
The implication of the second example is that he or she was going either nowhere or somewhere else sometime before the phrase was uttered. Note that the translation of this suffix may be English become or begin to.
Using this suffix implies that an action had been taking place, then it stopped, and then it began again.
vInejqa' I am resuming the search, I am searching for him/her again (nej search)