No. Cables don’t have internal circadian rhythms telling them what time of day it is

We are missing a bit of context for the data represented in the picture, but this could be an issue on the ISP equipment upstream of you (perhaps the devices are being overloaded by processes around these times) or it could be an issue on the line itself. A while back there was a post where someone suspected their cable internet was being used by a neighbor (if you live in an apartment building, this can be a concern). I believe the issue was tracked down to no MoCA filter being used in line. Alternatively, and this is probably more likely, it could just be a computer issue. You may have a lot of automatic computer processes running around that time, which may put strain on your allotted bandwidth.

what software/site did you use to produce these graphs?