that is rough, but before you write, I think you should spend time with your characters and get to know them. You can draw them in situations, or write short stories for them. I also like talking about them to friends, which we bounce ideas off of, and it can lead to some pretty great inside jokes. Sharing ideas with people and seeing them get excited it a big boost in the motivation department. Another thing you can do is rp with the characters or play dnd with them. I think it helps flesh them out, so that you can see how they would respond to different situations. When you spend time with your characters you should be able to answer questions about them such as: What do they like, what can they not stand and why, what colors they like and why, what is their motivation, How can you break down their personality (sassy, timid, etc...) And where do they live? What kind of world so they live in?
Then I would started working out stories for them. This process takes time, and I have a lot of story fragments form my characters that I chose to abandon and take a different paths. It takes time, and sometimes I will just lie on the bed, or couch just thinking about it.
If you don't think your plot is engaging, ask yourself why? What do you think makes you feel that way? Is it the setting, tropes, genre, etc... Spending time thinking critically will help you out a lot.