You have to remember a few vital things about ISTJs to actually have a relationship with one of them. As introverts, they need their space and alone time to function properly. And they tend to prefer long-term relationships and don’t want to waste their energy on flings. They can have a hard time establishing emotional connections with other people so be patient and don’t push towards anything they’re not ready for. The main thing is that if they want to commit to a relationship with you then it will happen.