[CaliforniaKarl]

Just to confirm: Within the last few weeks, have you started using a VPN, or TOR? Cloudflare is known to pop up captchas regularly for TOR users.

One other thing to check is, what is your computer—or other computers on your network—doing? For example, if all your stuff is behind a NAT router, and one device has been compromised, then Cloudflare may be treating your public IP as a problematic one.

Or, if your public IP is assigned by DHCP, maybe you got a problematic IP issued to you.

It's kindof hard to tell, as (as far as I know) Cloudflare doesn't provide a way to look up the status of an individual IP address (compared to how, say, Spamhaus).