I keep thinking about a woman from my old job

I keep thinking about a woman from my old job and I don't know what to do with it. Haven't seen her in four years. We worked together in a call centre in Cork. Nothing ever happened. She's married now too I think. I'm 38 married 12 years two kids one dog. Wife is brilliant honestly. Works as a teacher in Belfast we moved up here three years ago for her job. House in a estate near the lough, neighbour two doors down has a brown labrador same as ours which is mildly annoying because they get mixed up. The thinking started after I saw her on instagram by accident, she came up in a suggested follow list. I didn't follow her. But I've looked at her profile maybe six times in the last month. She's in Limerick still. She has a son. I'm not going to do anything. I know that. But why am I doing this. Why am I a 38 year old man hiding in the spare room at 11pm scrolling someone's instagram who I haven't spoken to in four years. What does this mean. Does it mean my marriage is in trouble. Does it just mean I'm bored. Does it mean I'm a creep. I genuinely don't know.