I have a 1994 Bonneville that sat over the winter. When I parked it, it had plenty of power and ran perfectly fine. It seems like it'* low on power, when you stand on the gas it won't jump into passing gear. It also dies every once in a while when you get off the gas while your approaching stop signs or stop lights. It always starts right up and you can go on. I also notice while sitting in my driveway over the weekend that the idle throttled up to 3,000 rpms for a few seconds and then came back down. It seems to run fine once you get going down the highway.

Any ideas without me having to take it to a mechanic?

I'm thinking it'* either your TPS(Throttle Position Sensor) or your MAF sensor(Mass Air Flow)
Do you have a multimeter?

Clean the MAF, inspect and test the coils, change the plugs, check the plug wires.

Do these cars have Idle Air Bypass valves? This was a common problem on Ford'* 4.6'*.

MAF was the problem on my 97. This also threw the SES light too

At a stoplight, the pcm will be controlling idle through the IAC based on MAF readings etc. While you are cleaning the MAF, clean the IAC as well and check the throttle plate/linkage for free movement.

You might check the air filter as well to ensure no critters piled nuts in there that might restrict airflow.

If it sat for a while it could be the gas try a new fuel filter and fresh tank of gas.