Lingering thoughts refer to thoughts or ideas that persist in one's mind, often unresolved and causing a sense of unease or uncertainty. Full definition
People with a strong sense of sentimentality are less vulnerable to feelings of loneliness or lingering thoughts about death, according to a series of papers published in the Journal of Experimental Social Psychology. (canadianbusiness.com)
«Puzzles easily distract you from lingering thoughts, and you can stop at any point. (mindbodygreen.com)
However in the past two years I've had this lingering thought at the back of my head, wondering what I would do if I were Arsene Wenger. (justarsenal.com)