Chevy Trailblazer 2004 (101,000 miles) Rough idle, shuddering, wants to stall off stop and low speed

2004 Trailblazer 6cy. 2WD - has been experiencing a very rough idle, engine shudders - no matter how long it’s been warmed up. Wants to stall off red lights and at very low speeds. Not throwing any lights yet - but the speedo is out (typical problem for this car) so I don’t trust the console for lights. Worse when the heat or air is on. Rides fine with more gas/higher speeds. Definitely worse in colder temps but continues even after 40-50 mins of driving. I’ve heard a number of things, but can’t afford to fix them all. I’ve heard plugs, dirty throttle body, cam shaft, sensors, cam actuator solenoid, etc. All seem to have people who said it fixed and didn’t fix the issue. Worried I’m going to stall pulling off a stop and rear end someone any day now. Where do I start!?

I would suggest replacing the plugs to start with. According to the maintenance schedule, these were due a thousand miles ago.

I “second” Pete’s post. I’d even suggest that the recommended 100,000 mile plug changes is too long. Use only OEM replacement plugs.

I’d suggest also changing the air filter at the same time. And bringing the rest of the maintenance u to date.