As Stephen King will tell you, writers rarely ask each other where they get their inspiration from because we don't know. The more we think about it, the weirder it becomes, so we tend to take it for granted that the ideas will flow.
Some of us find inspiration comes more easily than others. There's this horrible thing called writers' block that gets in the way some times.
I'm very fortunate to have worked with the brilliant and insightful Barbara Turner-Vessalago for many years now. She has taught me the process that I use whenever I write. It doesn't matter what I'm writing, this really works for me.
Most of the time, I'm writing a novel. I used to think that a novel was an enormous almost never-ending task. I was often so daunted by the immensity of it I would feel like giving up. Then I learned that any piece of writing has to be written one word at a time. One word isn't so difficult to do. The next one comes even easier than the first and I'm away.
My starting point is almost always a place into which I parachute my characters and allow them to have a good look around. Then I see what happens and write it down.
Barbara's writing process is called Freefall and I heartily recommend it to you. I have found that most books on writing craft only become useful when I've more or less finished what I'm writing and am looking for technical assistance to make it work. Freefall is so wonderful because it gets me going. Starts me off. I lower my self into a time and place, sniff the air, listen to the rustling of the wind in the trees, narrow my eyes against the setting sun and...
I think you've got the picture.
Until recently, the only access to Barbara has been through her workshops in Canada, Australia and two per year in the UK. I'm lucky in that I've managed to attend at least one a year since 2007. Now, she has published two books on Freefall. Get them. You will find them useful and inspiring.
https://www.amazon.co.uk/Writing-Without-Parachute-Art-Freefall/dp/1908363045/
https://www.amazon.co.uk/Freefall-into-Fiction-Finding-Form/dp/178592172X/
At the moment, I have the fourth Jenny Parker novel away for copy edit. The two Tyrant fantasy novels are sitting in a proverbial drawer maturing and my SF novel, Voyager, has just reached the 30,000 word hump which means it's now got a life of its own and all I have to do is watch what happens and write it down. So I've taken a couple of weeks out to write a radio play. This is really good fun and a complete change to my usual form. As a prelude, I attended an inspirational one-day course presented by a radio producer called Polly Thomas. If I like what I produce, I'm going to actually submit the script to the BBC, who sent me the only rejection letter of my career in 1972.
Wish me luck.
