The first few sentences, nay, the first few paragraphs you write, don’t be scared of them. They are going to suck, but their purpose is to get you back in the moment of your writing, back into your characters heads. They can and more often than not will be filler. They still have a purpose. Stop berating yourself about their unflattering appeal and that they don’t shine the way you want them to. Later, when revising, you can cut them or forage them for their shinny bits. They may be all exposition, world details. You can take them out and fold them into the story in a more natural way. But for now, let them be and keep moving in that first draft.