I have a 2001 Chevy Blazer 4WD and last couple days driving home on the freeway my check engine light starts flashing when i accelerate to 80 mph. once i stop at a red light and shut off the engine and restart it the light is gone. Why would it be flashing like that?

 

you need to get it scanned at autozone to figure out the codes.
Flashing = bad most of the time.
Although I did have mine flash before and it was just a disconnected vacuum line.

 

only does it if i punch hard on the gas and accelerate to that speed fast, but like i mentioned as soon as i turn off the car it's gone and normal driving conditons never bring out the check engine light.

 

Hmmm...sounds like you are getting a bad misfire. You don't hear any pinging, do you?
Can you make it happen in the driveway by revving the engine?

 

Hmm... Replied, but it disappeared...

Anyway, a flashing CEL means there is a potentially damaging misfire.

The diagnosis starts with getting the codes read. There should be pending codes and/or history codes present that will give some direction to your diagnostics. Everything should start with getting the codes read even if the light isn't currently on. And try to resist the urge to buy whatever sensor may be named in the code description. A code for a HO2S (heated oxygen sensor) doesn't necessarily mean that the particular O2 sensor is bad.

When was the last time a tune up (plugs, wires, cap, & rotor) was done? Were AC Delco parts used?

 

You should not operate the vehicle if the CEL light is flashing. A malfunction is occuring that may be causing engine damage.

You need to have the code read or purchase a quality code reader yourself.

Flashing = Bad ALL of the time.

In the mean time...Dont create the condition that causes the light to flash. You might be doing damage.