My son’s 99 Taurus didn’t want to start. At first thought it was a dead battery because of something left on, but jumping it didn’t help. It starter was clicking like the solenoid was going out. Finally it did start and turned over fast like there wasn’t a problem. I shut it off and restarted it again, no problem. Tried it a 3rd time and it wouldn’t start again. Sometimes it clicked when I turned the key and sometimes it wouldn’t do anything. Finally I had the wife turn on the headlights and turn the key while I stood in front to see if the headlights dimmed. The first time she tried it, the headlights went completely out. Not just dim, but completely off. The car started just fine after that and has been starting just fine ever since.
Any ideas on why this is?
Clean the battery, ground cable connections and the starter connection. Sounds like you have a corrosion issue. With enough juice applied you can temporarily get it working. It is likely to come back. Also pull the battery and take it for a free test at the autoparts chain nearby. It maybe a bit short of cranking amps.
I should have mentioned I cleaned the terminals off in the process of trying to get it going. They were all clean, though, when I pulled the connections. That made no difference. I should also mention that when it did start, I was no longer jumping the battery and the headlights no longer dim or turn off when I start it now. Not even a little.
At this point I would still pull the battery and starter. Take them to a chain store that tests them for free. I went through three starters from my local chain store before we found a bad battery in my 2003 Taurus. It is a really puzzling issue I know but at this point you are not sure that it will start next time. It has the issues of a flakey battery, IMO.