Hi, i have Coinbase wallet installed but keep wondering where all these unknown payments suddenly came from every now & then?

Since the amount is higher than dust threshold, at least the purpose isn't advertising or weaken your privacy. But there's no way to determine who's the sender without additional information. Why don't you try to remember if someone plan to send you Bitcoin.
P.S. if you have additional question, please make new thread instead and provide more info if possible.