How can you write when you're feeling totally uninspired? Lack of inspiration is not a medical condition, or something psychologically wrong with you- it's a wall you've subconsciously constructed between your creative mind and new ideas. Inspiration comes to you when your mind is open to thoughts that strike you from everyday occurrences.
So how do you open your creative mind to striking thoughts? Start by looking at something in the room you're in. I mean, really look at it. Here's an example:
Right now, I'm looking at my cluttered bookcase. I have a shoebox of photos, sitting on its side. The lid is slightly tipped off, which gives me slight anxiety that the pictures inside might fall out, or might be sitting in a wonky way and getting damaged. I wonder how long they've been sitting in the position they're in- maybe over a month? When was the last time I took out that box, or adjusted its position in any way? Have the photos been irreparably damaged, or is it something a mere couple of nights under an encyclopedia could fix? Now I have an image of a young woman laying photos out on a clean patch of floor, and stacking encyclopedias on top of them. Why does she have encyclopedias? Who has encyclopedias anymore? Maybe she's much older, and she's more comfortable having her information in text book form- or maybe she's an eccentric millennial? I look at my own hardwood floor- it's similar to the one she places her photos on in an obsessively meticulous way. Why is she so obsessive? Is it because she grew up with drug addicted parents, and she compensates for it by trying to maintain control over her life? Or because she grew up traveling with the circus, and her best friend, the lion-tamer, taught her that photographs are the eyes into the past.
(Okay, that last part was a little weird.)
You don't have to write a movie about an eccentric, meticulous millennial who was raised by a man who eats fire, but you've just had a vision; a vision that can blossom into new ideas and inspiration. You have opened the door to your creative mind. Allow yourself to wander. Allow yourself to be struck by new ideas inspired by everyday occurrences.