You might want to so some basic system maintenance before delving too deeply into this.

Restart, not just turn off and back on, your computer to make sure that any Windows updates have installed.

Clear your browser caches. I use CCleaner to do this.

Run SFC /SCANNOW from an elevated command prompt to check and repair your Windows install.

Run HWMonitor to check your temperatures, CPU and GPU speeds and loading.

Maybe, run something like Memtest86 to check your RAM.

Make sure that your anti-malware apps's security settings are not so maxed out that they are slowing things down.

Shut off any VPN that you may be using.

Run a speed test to see if your Internet is actually as fast as you think it is.

After this you might want to have the security people here check your computer for more insidious malware, like maybe a rootkit Bitcoin miner. I found one of those on my system after the tech support of a major gaming company "helped" me with a game crash issue, which turned out to be caused by one of their botched updates.

 

You might want to so some basic system maintenance before delving too deeply into this.

Restart, not just turn off and back on, your computer to make sure that any Windows updates have installed.

Clear your browser caches. I use CCleaner to do this.

Run SFC /SCANNOW from an elevated command prompt to check and repair your Windows install.

Run HWMonitor to check your temperatures, CPU and GPU speeds and loading.

Maybe, run something like Memtest86 to check your RAM.

Make sure that your anti-malware apps's security settings are not so maxed out that they are slowing things down.

Shut off any VPN that you may be using.

Run a speed test to see if your Internet is actually as fast as you think it is.

After this you might want to have the security people here check your computer for more insidious malware, like maybe a rootkit Bitcoin miner. I found one of those on my system after the tech support of a major gaming company "helped" me with a game crash issue, which turned out to be caused by one of their botched updates.

Thanks for the quick and comprehensive reply.

Interestingly, this morning my Internet browsers seem to be running better. At least that's my tentative impression.

Something I neglected to mention in OP is that, yesterday, when I ran the Internet Connections Troubleshooter (found in "Settings"), my connection was fine but I did get that "...Network Adapter not connected..." or "...Network Adapter not working consistently.." error message. This morning, I am not getting that same message when I run the Troubleshooter. Maybe this means my problem has self-corrected?

I propose that we shelf this issue for 12 hours, just to wait a bit and see if the problem has resolved itself. If not, then I will proceed to execute the tests and steps you recommend. Assuming we get that far, I will need to ask for specific step-by-step instructions regarding the technical tests and repairs you indicate.

This evening I will post a comment explaining my status. At that point you can close this ticket if everything appears okay with my system.

 

Windows is pretty good at monitoring and correcting itself nowadays. Oftentimes a reboot will allow it to do some housekeeping and fix minor issues. I forget to ask whether or not you'd run the Networking troubleshooter too. Just right-click the icon on the task bar and select it.

Delving into the Event Log is beyond the scope of my capabilities but it will oftentimes tell you exactly what is going on with your system. Maybe someone here can help you with this. If you want to look around, just hit Winkey-S and search for Event Viewer.

 

You can choose to Solve this thread when you are satisfied, no one will close it before that.
Your ISP may have had an issue yesterday.
Check your internet speed Speedtest by Ookla - The Global Broadband Speed Test If it is less then the advertised speed, then contact your ISP to test your lines.

 

You can choose to Solve this thread when you are satisfied, no one will close it before that.
Your ISP may have had an issue yesterday.
Check your internet speed Speedtest by Ookla - The Global Broadband Speed Test If it is less then the advertised speed, then contact your ISP to test your lines.

My Internet connection has been perfect all day. The problems I experienced yesterday have resolved themselves, it seems. I think I'm all set.

If the problems reoccur in upcoming days, I'll update this thread. Meanwhile, thanks for your input.