I would also throw in that before starting the mold up it might be worth purging out the manifold with fresh material just to make sure the material left in the manifold and drops are not degraded, this would help get you to have better startups.

If this is from a degradation issue it might be worth reviewing the residence time of your material, ensuring you are using the correct barrel size and not one too small, and ensure that your melt temperature is higher than the recommended range for the resin. Looking at the actual melt temp of the melt while it is running would be better than basing everything off of barrel temperatures.