Shooting new work and composing series is never a straightforward, linear affair. It's never a string of productive days that ends with something to show for. In fact, just like shooting, a lot of it is waste and irregularly paced. It has bouts of intense activity followed by periods of maddening inertia. It's cyclical and you never know how long the current up or down will last. It may seem obvious now, but it took me a while to accept the idea that a constant level of output is not sustainable or even desirable. As in music, the silences are part of the music, not bookends around the melody.
When I haven't produced anything for some time, the best thing to do is to give it some space. Leave the unfinished editing, the print lists, the cameras, and come back later. It's ok not to do anything at all for some time, sometimes the only way to get back to photography is to not be doing photography.
Fields and trees aren't dead in the winter when they're not continuously blossoming, the entire winter is a preparation for spring. Sometimes it's shorter or longer than usual but it can't be rushed.
As unpleasant and frustrating as it can be, inertia can also be where breakthroughs happen, when I run into the limits of what I've tried so far and I'm forced to think of new elements and methods outside my habits to get out of the block. It's hard to describe how the thaw comes, but in my experience it can only be slowly encouraged, never forced.
I keep notes of each week's progress, things like how many rolls I shot and how many prints I made. They serve as a reminder that despite how it seems, I have in fact been quite productive.
I set specific and realistic goals (e.g. shoot one roll of film a week). It should be an easy threshold to clear, the idea isn't to shoot masterpieces but overcoming inertia.
In shooting, I'll try a different focal length for a month, a different emulsion or even colour or a different format. I'll try to go off my usual paths to have new and different things to look at. If I've been shooting mostly during the day I'll go out at night, I'll bring my flash or a filter. Repetition is the specific challenge here.
In printing, I'll put it aside and do contact sheets for a few sessions. Lately I've been having a lot of fun with small 5x7" on RC paper, they're quick and fun to make. I'll spread a long print list into short sessions of a few hours over a month with alternating weeks of no darkroom days. Wanting to do too much is the specific challenge.
If I'm editing, then I'll switch to a different project. Or I'll shuffle the order to force a new perspective on the set. I'll timebox editing sessions to one or two hours then get up and do something else. The feeling of not doing enough is the specific challenge.
I don't subscribe to the idea that one needs to find inspiration in order to make things. It helps but it's not a requisite.
New ideas can come from many places. They can be a result of being confronted with the limits of what I've been doing lately, in terms of process or subjects.
I also find new ideas in watching films and photo books.