Firstly, I'm kind of a noob like you so what I'm about to say is no science, just my own experience. I think you have a nice sounding voice. But I think you need to open your mouth more. Like a lot more. I've been told the same thing. I used to sing in the office when I was alone. But you always have the risk of people walking by, so I sang just like you. Close into my phone, hunched up and really singing for myself and afraid. So what really helped me is singing in my car. I got in my car and sang during traffic jams or even at empty parking lots. Your car will be the private place where youcan let loose and experiment with tips you find online. And dont forget to record yourself.
Lastly I started the TVS course. It has a lot of info, I cant say for sure how much it will improve me, bceause I just started. But at the very least it's very promising. Its on Udemy.com and its 10 bucks for a limited time.
Hope any of this helps!