I’m not sure how to check my single levels
Go to 192.168.0.1 in a browser then login with username:admin password:password(unless changed). Then click on Connections on the left, then click on Cox Network. Scroll down a bit and you should see your downstream and upstream levels. Unfortunately I don't think the gateway displays the event logs that might show why the modem is rebooting but Cox tier 2 should be able to read them remotely.
COX pushes software updates that seem to always break things
That is why I don't recommend using the Cox Panoramic gateway if possible. Not only do you have to pay monthly for it, but I find it's performance and features to be lack luster. Without owning your own router, you can't control the firmware. However that may have no relevance to your problem.