No Power (it's like the battery is out when I go to start the car)

So I just put in a new water pump, and the car started up just fine. I let it idle for a little bit and then added more water and then I turned the car off to check to see if I could hear any leaks. When I went to start the car it won’t start. So I turn the key a little bit and my radio and all the gauge lights come on like they should. When I turn the key farther to start the car it like there isn’t a battery connected at all. It’s weird. In order to get the lights to turn on you have to go and disconnect the negative side of the battery and then reconnect it and the same thing will happen. When I turn the key partly on I can hear my fuel pump prime. It’s like everything is going to work. Let me know if anyone has any ideas. It’s a ls vtec all motor

Make sure your battery terminals are tight and clean.

Do you hear a click when you turn the key without the engine rotating. Bad starter or ignitor.