Novice help please!

I just got a Sigma 56mm because I’d like to focus on more portrait photography, family stuff, I’m a novice. My Sony prime lens that came with the camera was just not cutting it and I was getting consistently blurry photos. Well I think I’ve maybe gotten 3 sharp photos from this new Sigma lens. Im so frustrated to the point of giving up. Ive set in A priority, auto, S priority, Auto ISO, etc. Set to auto focus, center weight. These first two photos were taken this morning at our dining table, one about 4’, one maybe 5’ from me. The third clear photo is when I turned the ISO up to abt 12,500. Is that the issue? Because I’ve tried that as well and not always had the same result.

What am I doing wrong? Any help is so much appreciated.