Everyone understands how emotions can cause tension. How a character feels is often how the reader begins to relate to the story. Certainly, relationships between characters can cause stress. Other circumstances factor in, too, like finances, toxic work or family environments, abuse, loss of a friend or loved one, failure at an assigned or desired achievement, all of which can lead to feelings of unworthiness, worthlessness, anger, frustration, hopelessness, and more. Plus these feelings can develop unhealthy ways of coping with them. All these situations can create tension for the reader, so starting with characters with problems is one way I try to create tension.
A character's self-concept also plays into emotions. That character's self-image can include their mental image that affects their self-image, their status, strengths, and beliefs. If a character's self-image is confronted in a story, it will affect them mentally and emotionally, and situational or emotional tension will also be involved.
Situational tension is a huge aspect of how the plot leads the character into the story's purpose. People react differently to each other which often leads to opposition, dislike, hostility, and even personal danger.
Environmental factors that give tension to a story include locational dangers and hazards both nature and human-made. The world has many locations that are dangerous such as trying to climb Mount Everest (or any other mountain) to even an avalanche while skiing in a resort, or being stranded far from any help. People have developed their own dangerous situations from work sites like buildings under construction, chemical plants, or even events like Texans suffered in February--unusually bad, freezing weather leading to no electricity, no heat, and broken water pipes all during an epidemic.
So, developing tension isn't difficult but not repeating similar situations in other books sometimes becomes a problem.