Having to reboot Modem to fix 10-30mpbs speeds

Yo,

Having to reboot modem 2-3 times a week due to gigablast service slowing down. Speeds always seem to be at 10-30mpbs when it happens. Only rebooting the modem brings the speeds back. Speeds are tested via ethernet. Connection at the outside box and in the home have been checked for loose connection. Tried a few different modem brands, That didn't help. Ive seen a few others having a strange slow down to the 10-30mpbs speeds and having to reboot the modem to fix. Would my modem logs glean any info to diagnose the issue?