Bad news (full disclosure) I am not sure what may be happening.
Good news: you have options to try.
First, run the built in Windows trouble shooters - they may identify and fix something.
Second, try another known working Ethernet cable. (Which you may have already done per your reference to "reconnected the cord....".)
Third, which becomes somewhat more involved, is to use Task Manager, Performance Monitor, Resource Monitor, and Event Viewer to watch your system and see if any of the four tools present or capture something at the time of the drops.
Event Viewer is the most likely to have captured something. Just a warning or informational event in lieu of an error.
Some situation where internet connectivity is lost but not to the point of being unrecoverable.
Open one of the tools, leave the window open but set to one side. Work as normal and watch what you system is doing.
Could simply be some faulty app trying to "phone home", failing, and causing your PC to lose connectivity in the interim....
Key is being methodical and having some patience.