I am having the same issue. My modem was powered off for a week since I recently moved and then upon starting up after moving, this constant reboot seems to be happening. Looks like the modem is not happy with whatever the new firmware upgrade its been sent. Who can help?
Check out this post as well (marked answered)
Yep saw that. Unfortunately, none of those worked in my case and I got tired of talking to Linksys / Comcast and ended up getting a new modem