HELP:Ignition Problem 1985 GMC High Sierra

[SnowNeck]

Alright so i have a 1985 GMC high sierra, and not until recently I've been having this starting/ignition problem. so when i go to start my truck wether its been sitting over night or just a few minutes as i get gas when i go to turn the key to start it... Nothing no clicks, im getting no power. so i knew it the battery well thought anyway. i got a brand new battery and same thing. happens every time i go to start my truck. what ive been having to do is take off the Negative wire from the battery, and put it right back on and it starts. i don't get it at all, im not shacking any loose wire just taking it off and putting it right back on. i don't have any rust, corrosion, anything. I need any thoughts on what this might be, this is my daily driver so its important. thank you.