1997 Dodge Intrepid Car starting after several tries

1997 Dodge Intrepid 6 cyl Automatic 114000 miles

I just got this car last week. The guy I bought it from said it had been doing this for at least a year but it never quit running so he didn't bother to get it fixed. He said he thought the starter needed replaced (had a flat spot), so I was gonna get it replaced but took it to Auto Zone to get tested before I did.

The problem: When I start my car, it just clicks. It can take a few times up to about 15 tries for it to turn over and start. First thing in the morning takes a long time. After it's run all day off and on it starts first try or after a few.

When I took it there I had them check the starter, alternator and battery, as well as my check engine light that goes on and off all the time. The starter he said was fine. The alternator and battery were both a bit low but he said that could be because the car was sitting for months before I bought it. The check engine light he said was caused by my oxygen sensor not working. He said this could be caused by junk build up on my battery terminals or falty wiring to my starter, and to have both thigns checked. I'm gonna have someone check these. But I was wondering what your guys' opinion of what could cause this is?