Baby moving at certain times

So I’ll be 17 weeks on Friday. I’ve just started (or at least I think I have) feeling baby move. Kind of feels like throbbing in my lower abdomen when I feel it. Like little nudges coming from the inside. If what I’m feeling is correct and it is baby, I only really feel in the evenings when I’m sat down on the sofa watching TV. Could this be because that’s when it’s mostly active or because I’m laid out with my legs up more stretched so I can just feel it more? TIA x