I feel to get around the problem of when to stretch we should do mobility exercises before we go out for a run. Mobility exercises will help because they will use large muscle groups, which will get warm, increase heart rate slightly, warm up the synovial fliuid in our joints , help get us mentally ready to run and warm up our tendons and ligaments.

The difference between mobility and stretching is that movement is used in the mobility exercises whereas stretching is usually a static exercise.

See attached video for a routine.