Starter problem

when i go to start the car i get a click and than a start, this gets worse over about a weeks time than there is no problem for about a month it fires up perfectly , whats up a loose wire ?

Could be starter, battery or poor connections at the battery or starter.

Remove the battery connections and clean them along with the battery posts using a battery post cleaning brush. If that doesn’t fix the trouble then the starter solenoid contacts or main battery cable to the starter may be corroded.