Big Bear wants to start when positive battery cable attached?

I have an 87 Big Bear 350. The battery failed so I got a new on, went to install it today. And when I attach the positive battery cable the starter cranks, even with the switches off. Negative
cable is attached. I had the leads for a winch and sprayer attached, but removed them to eliminate them and it still does it. I’m assuming there is a short somewhere. Can someone point me to where I should be looking.
TIA
Bob