If you're not using a mid layer between your wool base layer and your Shower's Pass shell, that's the problem. Sounds very counter-intuitive, but it's true, and a much better jacket also worn over a base layer but not mid layer will do the same thing. Invest in a cashmere sweater, or a fleece, or a softshell.

Your base layer's job is to move your sweat outward. Your shell can only let so much vapor out, and, once it's at its limit, this starts to condense into drops of sweat, and then it's trapped. You'll start to feel clammy, which is cold in its own right, and, when you stop, like for a red light, your body will try to produce more heat to compensate. An insulating layer puts an end to that, and helps deal with the sweat, away from your body, keeping you nice and comfortable.

Cashmere wool (from goats, not sheep like merino) loses most of its insulating power temporarily, when it gets both warm and humid, which is what happens immediately before you begin to sweat. No button necessary.

I have a new balance running jacket that I use for cold rides. It is a thin knit fabric with windproof nylon on the front and top of sleeves only, works well. Layered with a polypro base and then a wool layer. 38 F to at the start today, 18 miles and 1.25 hours. Warm, mostly wind proof and a little sweaty when done. Have you looked at running/ cross country ski type stuff ? I think an insulating soft shell with gore wind proof or something like that would be a good fit. I have gore wind stopper gloves that work great.

I use a simple Sierra Design thin nylon wind jacket not made for cycling, although it does have a longer tail. It predates so called "softshells", breathes and has a back vent. The collar is quite large so I can fit a neck fleece tube inside.

I use my showers pass elite 2.0 rain shell over my insulating and base layers. Works great. similar scenario for the legs, too.
Once the temps are below freezing I add a thin balaclava that I tuck into my mid layer, and it helps keep the drafts from coming down my neck.

Pearl izumi elite barrier. Windproof, water resistant, converts to a vest, so yellow it hurts your eyes to look at. Been commuting in high 20's with this and a wool underlayer.