I have a '98 silverado... I was recently just driving down the interstate and the check engine soon light popped up to the left of my odometer... this has happened to me before while i was driving on the interstate, but it went away after a day...any idea what caused this and what if anything i need to do about it?

You need to have the fault code down loaded from the PCM to begin the trouble shooting process!

I hate to say it, but the Dealer is your best bet.