What may be causing light gray horizontal streaks across my computer?

Are the going down the screen.. If so you just need to adjust your refresh rate. You can do that by going to your Monitor settings in the control panel. Adjust it to a higher or lower Hz. Hope this helps..

They are not moving down the screen, but I’ll try what you suggested.

Thanks Fallstand. I tried to adjust the monitor HZ settings up and down with no corrective effect. Still open to suggestions as the situation continues.

Could be that your monitor is almost kaput. Does it happen if you switch monitors?

Also could be magnetic interference? Maybe??

Does your monitor have a degauss button or menu setting (usually looks like a magnet with a squiggly through it)?

Thanks andrew/ Yes I did try the degauss button with no effect.
I don’t have another monitor to try and you may be right that the monitor is going out. Hope not.
I am connected via cable as well as is my digital phone and TV for some several years and this is the first time I’ve experienced this kind of situation. Interesting aspect about magnetic interference. Maybe I should check with my cable carrier – Comcast.