Hi Karl. Why stretch before a run when your muscles are cold? It only increases your injury risk. Post run muscle soreness is not a bad thing per se - if you've done an intensive session, you should expect to be slightly sore. The best way to deal with this is ensure your body receives a good dose of carbohydrate and some quality protein, within 30 mins of stopping exercise. This should reduce the effect of DOMS in a way which stretching never will be able to do.
If I was to say there are two stretches which are typically neglected by runners but of high importance to injury avoidance, that is to do a stretch of the Soleus muscle (the hidden muscle deep in the calf), and the Piriformis muscle (goes laterally in the butt and stabilises the hip). A third muscle/ tendon to stretch (but not everyone is affected by this) is the Illotibial Band (ITB for short).
You can easily find stretches for these on the YouTwitterSphere. Good luck. 