2002 E53 3.0i Intermittent no crank/start

[DaveX53.0i]

So i’ve looked around the forums a bit and haven’t really seen anybody talking about the issue i’m having. If I may have missed it, feel free to link the forum below. I’ve got a 02 E53 3.0i with 175k miles. The issue started around the same time last year (December in Maryland) and pretty much stopped around the spring so I haven’t fully ruled out the cold but i’d prefer not to have to deal with this everytime it gets moderately cold. I’ve found a way of dealing with it, which i’ll mention soon. What happens when I get in the car and try to turn the key, turns all the way, all of my dash lights come on, interior lights work, hell even my stereo, amp and sub work but it doesn’t crank, it makes one single click when I turn the key completely. The way i’ve found around it is to pop the trunk, unhook my sub, open the spare/battery hatch and lightly tug on the positive cable, it doesn’t always work after one light tug but it always eventually will allow me to go back and turn the key and it’ll start right up. Before anyone asks, no the terminal is not loose, it doesn’t budge on the battery even a bit. I don’t believe it’s a faulty BST (am I getting that right? it is a BST correct?) because as far as I know the vehicles never been in an accident. Does anyone have any ideas? I will say I haven’t checked any fuses yet... probably should have