Engine Vibration! Help please...

I am new to these forums and car stuff for that matter! I know what general parts are and can hold inteligent conversations about cars but when it comes to working on them, I only know the basics and nothing about internals.

Problem:
I just started up my intigue (99' 75,000mi) today and the engine has a slight vibration to it. When reving it goes away in park. Then in drive or reverse it is worse, vibrating to the point that I am scared to drive it. Then it is still there when I give it gas. When in neutral it still vibrates so it cant be the tranny, right? What should I do?

Thanks for any help.

BTW I am going to do the oil change and the spark plugs tomorrow.

After a couple starts the car went back to normal!!! The computer must have adjusted for something. It is still wierd that this happened. Does anyone have an idea of what could have happened?

My '98 3.8 76,000 miles engine had the same thing happen this past winter. I shut off the engine and the next start it was a little better so I drove it to Autozone. The codes read random miss-fire on cylinder 1. It hasn't done it since, however, in the mean time I had the oxygen sensor replaced, Fuel pressure regulator, and a new wire set to help eliminate a hard starting issue. I beleive my problem was low gas and the engine wasn't getting enough because it possibly froze. Try throwing some Lucas Tune up in a bottle in your gas tank. It's available at Autozone.

I have a short ram air intake installed. Do you think that maybe the sensor on it wasnt reading good at that time? How much is it to get a reading from autozone?