Someone on your network constantly searching on google can be people or software, or extensions. The constant search like that makes Google suspected you are the machine, not the person should force you to enter captcha.
How to fix
- One is waiting for it to go away.
- Two to reset the modem again. If your network is not using static IP then reset the modem. You will be given a new ip will not be caught catcha google anymore.
However, you should also check if your browser has any extensions, or if some strange software is working.