2002 Chevrolet Trailblazer 02 Chevy Turn Key Switch On You Clicking Sound There

I have 02 chevy trailblazer when I turn the key switch on all you here is a clicking sound. There are times it turns on perfectly and times when it doesn't. I also had put a new battery because it needed one but it still does the same thing.
One thing i tried was to hit the solenoid and have someone turn the key switch and it worked & turned on & off. Next day when to turn it on without hitting the solenoid didnt turn on. Hit the solenoid and it turned on. Please Help.