Low idle issue

I have been getting some periodic faults with the idle on my 1997 k11 1.0.

Car runs great 85% of the time, both when cold or warm.

But sometimes the car idles poorly, allmost cutting off. this happens both when cold, but also when warm (usually when restarting the car). but then after a short time (usually after driving for a bit) the idle is just perfect.

I did the resoldering job - didnt work.

Then i changed the temperature sensor - still the same.

changed the plugs - still nothing.

Any suggestions?
I get exactly the same though mainly happens upon first start up hot or cold then evens out ok.
I have re-soldered recently (it was really running like pig before I resolded). Though I am wondering if I need to do it again?
It's running ok otherwise, so am I not going to piss around with it until spring now!