I started having issues with my old computer a while back. The issues basically as soon as you turn it on. Almost always, the Dell boot up screen, instead of just being the usual blue against black, will be alternating 1cm. vertical orange and blue stripes. Sometimes lines, sometimes blotches of color will pop up and gradually worsen the longer I use the computer. Sometimes there will be, for instance, a pink blotch of color that follows my cursor around. Pretty soon, the screen will flash on and off. Pretty much always, the computer ends up freezing. This all happens so quickly that sometimes I can't even log in, let alone attempt connecting to the Internet. Video card? Motherboard? Update my graphics driver?
What are we dealing with here, are you talking about a laptop or a tower based system.
With a tower based system if it gets worse the longer it is used it is a sign of two things.
The cpu fan on the cooler is not working or is clogged and matted with dust.
Stopping air flow to cool the cpu heat sink.
The same result is also true if the system has an add in graphics card.
If you are talking about a laptop, then again if of a few years old. it needs to be opened and cleaned for the same reason dust clogging the cpu cooler fins behind the fan blower unit.
Or if a laptop, it can be a sign that the video cable to the laptop motherboard is dislodged or is worn with use as it passes through or near the hinges of the laptop where the screen folds down. And it may need a new video ribbon cable.
In most cases it needs a clean to remove dust that has collected over the years preventing cool air flow through the cooling fins to keep the cpu or graphics card chip cool.
I would check the cause first is dust build up, so it will need taking apart and cleaning.