Antihero
A wise man once said "Unsolicited Generousity is the Garnerer of Paranoia" To put it a different way, everyone knows people are selfish, so when someone is being unreasonably nice to you for absolutely no reason, especially an unfamiliar person you can't help but suspect their ulterior motives. Nothing is free and if someone is willing to give you the world you can only wander what they seek in return