How can I get this guy's attention again?

So there's a guy I work with who seemed like he was into me before, but he can be very hot and cold (he's a Pisces, if anyone answering cares about that). I am not looking for a relationship, but there's def an attraction. He's older than me and we get along, but it's hard to tell if he's interested anymore or not. Last year was pretty rough for me, so he met me during a not so great time in my life. I just started back at work and he has been nice, but I am having a hard time reading him. We haven't texted in a very long time and I'm nervous to bug him all of a sudden, but I miss the rapport we used to have. Even if it doesn't ever become physical, I still want us to be friends. I'm not sure how to break that barrier again and am not sure how to tell if he's interested. Since we work together, I don't feel comfortable being too forward about it (we work in close proximity and he has seniority over me but isn't my boss). I feel like he would have to be the one to let me know in some way that he's interested before I do something to embarrass myself. Like I said, either way I generally want to have a good rapport cuz I plan on working there for a few years. It seems like he's cool with me, but it also seems like he has a bit of a wall up. I fear that since he met me during a not so great time last year that he won't be able to give me the benefit of the doubt or start fresh with me. How can I get on his good side again, and how can I tell if he's interested in a potential fling without outwardly asking him?
(Yes, I know it's always complex with coworkers. I just figure if we have a good rapport and text a little more, I could just be starting the slow pursuit to low key let him know I'm down in general. I'd prefer us to not be coworkers if something sexual happens between us since we work so closely together, but that doesn't mean I can't low key lay down my interest before I don't work there anymore. He's the itch I really gotta scratch and I'm okay with waiting).
How can I get this guy's attention again?
Add Opinion