It's a two way street. She needs to communicate, too. You shouldn't be walking on eggshells trying to second guess her moods and motives. Depending on severity, that can be borderline emotionally abusive.

First, straight up ask her how her day was. If she is stressed or hurting, just straight up say, "I had something sexy planned, but you seem like you could use some cuddling and TV instead." Or maybe a backrub with no expectation of sex.

Tell her what cues she can use if she's interested in starting. Like, "nibble my ear and I'll take it from there". Or maybe running her fingers down your chest or stroking your arm. Whatever gets you going.