When I think of bridging as it relates to the feed throat area, I think of the section of the machine directly below the hopper and above the screw that sometimes gets a clump of material bridged across the opening preventing material from getting to the screw. From what you posted, I gather that you can see the feed screw, and it is the feed screw itself that has a section of bridged material. That being the case, I should think that it is either one of two things. During shutdown, the machine has not cooled enough before the screw was stopped, allowing the still hot feed section to melt the material into a large mass, blocking feed. That, or the start-up heating process is reaching temperature far too early prior to the start of the feed screw. In either case, allowing material to melt on the feed section of the stationary screw will cause issues.
Of course there may be other factors, such material moisture and throat section temperature. As in any trouble shooting problem, you need to look for what changed.
Hope that helps!
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