Start Up problem

That is probably a battery terminal/cable issue. I would replace the terminals and clean them with a wire brush. Side mount battery terminals are junk, frankly. Whenever there is a power issue, I replace mine because they only cost a couple of bucks and are usually the problem. You might also take the cables off at the starter and clean them up too.

How to clean the battery cables: https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

If that does not solve the problem, then you should probe the starter when it is in its clicking mood. Using a multi-meter, you will ground the black multi-meter lead and hook the red up to the red trigger lead going in to the starter, and then check to see if twelve volts are getting to the starter when someone turns the key. If there are twelve volts, then pull the starter and have it tested at the local auto parts store (they will do it for free).

Information about starters and how they work: https://www.2carpros.com/articles/how-a-starter-and-solenoid-works

Start simple with checking the cables and go from there. Let us know how it goes for you.