I've always used SAS, but right now I'm trying to get relatively simple unmanned rocket to orbit completely without SAS using gravity turn to finish one contract.
I've tried dozens and dozens of times with different design changes. I've tried lowering speed, switching to less powerful boosters, more fins/winglets, but it's unstable even at launch and rocket tends to tilt in one direction without me pressing any buttons.
I don't understand why, it is perfectly symmetrical, nothing special at all. If I try to correct course manually it is hard and very imprecise, at some point (usually when I detach boosters) I completely lose control and can't do anything. Right now it looks like this:
I've search all possible information, read several tutorials and can't get any solution. I'm really tired of this. What's wrong with this design?