when I pull plane from a heated hanger after preflight into -2 to -4 degrees celsius I get condensation on wing. Seems to stay liquid for a while. Do I need to be worried about this turning into ice and how quickly.
Yes you do. It is at risk for freezing before take off, at which point, you could lose a lot of lift. Something that does work, if you are unable to get the condensation off with a towel, is to use TKS in a garden sprayer to coat the area. Works really well. If you use that technique, make sure the TKS/water mix rolls of the wing, usually around 40ish knots, if it still looks like droplets it is probably frozen and that would be abort time. Wan’t supposed to freeze in Bend OR lat week, Oh well. Didn’t take my TKS sprayer so had to wait for the sun to come out. 
Chuck do you spray it on the wings including the boots? I was curious if the TKS fluid could harm the boots…
If it is all liquid and stays that way for a few minutes, I would consider keeping a box of high absorbency towels in the hanger and just wipe it dry.
Per Goodrich the boots are resistant to TKS. Some aftermarket boot cosmetic products may not be tolerant.
This is one of the many things I have tried in aviation and failed at. If it’s cold enough outside, when you start wiping you will thin the water enough such that the additional surface area created will freeze the water before it absorbs. Might not happen every time but be prepared for the possibility.
Yea, I can see that happening if it is really right on the edge of freezing.
Thanks everyone consistent with my thinking. Will be utilizing a little Tks fluid.
Methanol will also work. You could spray on your wings and wipe off the residual.
TKS is better, but sometimes I just use a weed sprayer ($10) and RV antifreeze $5. Melts the frost and ice, comes right off the wind on take-off (TKS causes a bit of drag too.)