Constant Bluetooth Connection Request Prompts Between Two Macs
Continuity and iCloud are the obvious paring agents, so I would disable handoff first on both devices and see if that quells things.

If so, you might need to engage Apple Support to see if there’s a precise way to rejigger that, but for most people you would need to sign out of iCloud on one or both Macs to then sign in again and see if the pairing identity crypto can heal itself.