I would say that the first step is to isolate the problem.
The only way you can do that is to hook it up to another computer to see if you get the same symptoms. If the symptoms are the same, it's a monitor problem. If symptoms disappear, it's a computer problem.
PJ, please return and let us know the results of your investigation.
I shut down the computer and tightened the cables on the back of the computer. No change. Maybe this is a wakeup call to get a new computer AND monitor. My computer is almost 4 years old and was thinking of getting another one next year. Anyway, despite the vibrations, the screen is still readable.
BTW, my big thing is to buy groceries at INCREDIBLY LOW prices. Like today I bought 4 packages of Nathans hot dogs for about $2.40 total due to a combination of sale and coupons. On Sunday evening, I bought a total of 12 Boston Market TV dinners for a grand total of about $7.50.
So perhaps if I look around, I can find an incredible deal on a computer (and monitor).