Shudder While Idle & +100km

I apologise if I ask any stupid questions, and 17 and know little about car maintenance/repair. (other than the basics)

So anyways... At random times (usually after cold nights/winter day) my 89 civic will shudder while idling. Sometimes it gets pretty bad, it just won't run smoothly. It will decrease if I give it a little gas but even so, I worry about the shuddering...

I'm not talking extreme cold, it could be cold one night and then the next day it will be +20'c and it will do it.

It will also do this at around 100 km/h...

I'm not sure what to make of it, could anyone please help...?
Suggestions or ideas... anything


Thanks...

possible bad motor mounts, engine misfire, exhaust rattling against the frame...!!???

mine does the same thing...but I have to replace my motor mounts. Just too broke to fix it.