Guys, here's my problem:

All power cuts off as soon as I try to start the car.
If I unplug the negative cable and plug it back in, the power comes back.
It then starts up fine but when I kill it and try to start it again, the same thing happens again.

Is the problem in the battery or somewhere else?

Thank youuu!

 

clean and tighten both battery terminals including where the wire goes into the terminals if you do not have the factory crimped on ones.

report back after trying that.

 

I did clean and tighten the negative terminal but not the positive one.
Will do that and report back. If that doesn't help, could it be an ECU problem?

Thanks for the help!

 

Remove the negative cable before tightening the positive. When you have a wrench on the (+) cable, it's too easy to short to ground. Lots of sparks...

 

pretty unlikely - you have the classic symptoms of corroded / loose terminals.

 

In addition to the terminals, check the condition of the wire. I've seen corrosion where the actual stranded wire is attached to the end-lug. Also have heard of where the wire itself is corroded & almost breaking, in the middle, inside of it's plastic insulation.