What are some strategies for writing when lacking inspiration or motivation? Is writer's block a common experience for writers?

Stop trying. Get away from your implements and go live your life. Come back tomorrow and try again. Writer’s block is a brain block. Read a book, go for a walk, whatever means not thinking about your work. Keep a notebook handy incase something comes but focus on not your work.

Other commons solutions are:

Keeping office hours. If you have an hour a day to write you must sit down with no distractions for one hour. Come back tomorrow and do it again. No tv no reading, just let your mind wander and think.

Write with a stream of consciousness. Sit down and write page after page of whatever comes out of your brain. The water can’t run if the faucet is off.

Write a book. Literally pick a book you like and type it out word for word.

Some assholes say, “It’s not real” and then tell you the most common ways to get over it. It’s like saying, “Migraine’s are fake! But take some Tylenol.”