2000 Carrera seems a bit nervous at speed

This past December I picked up a 2000 Carrera with just over 80K miles. I haven't driven it much thanks to all the lousy weather. There have been a few occasions when I've had the chance to get to 70+ on the highway, and the car seems tone a bit more twitchy than I expected. Hard for me to be more specific at this time. My Boxster always seemed super stable at speed. With the 996 when I'm going fast it seems that if I hit a bit of a bump or undulation the car gets a bit unsettled. Perhaps I should start with getting the alignment checked? Any other ideas? The Bridgestone tires are fairly new.

Worn out struts? What kind of tires are they? If summer performance tires than they don't stick well in cold temperatures this time of the year even in your area. Also given your past experience with P cars, assume you know how to read tire date codes to make sure the tires are reasonably "fresh".

Tire pressures are the easiest to check and correct if not right. Be sure the tires are the right tires -- appropriate sizes and the same all around -- and are all the same N rating and style/brand. If they are not N-rated (or even if they are) be sure the all the tires have the same load and speed rating, tread wear number and traction ratings. Be sure if the tires are unidirectional they are all mounted in the right direction. Inspect each tire for even wear across the face and feel each tire's tread face for any feathering/scrubbing sign. If you see sign of uneven tread wear or feel feathering/scrubbing roughness then alignment is suspect. Unless you have paperwork this was done before you bought the car I'd have this done almost regardless just to ensure the alignment's spot on. Note that an alignment on worn tires may not deliver the same results as an alignment done with new tires installed but I've had alignments done with used tires and the results have been quite good, dare I say indistinguishable from the new tire alignment done on the same alignment rack by the same tech I might add. When you have a chance get the car in the air and check the shocks for leak sign and just give the steering/suspenion/drivetrain a thorough inspection looking for anything amiss. You can also have an experienced tech test drive the vehicle and report his findings/impressions.

I had similar issues caused by lower control arm and or bad alignment. Once those were fixed the problem resolved.

Great post by macster, I'd vote for alignment since you noted that the tires are new Bridgestones.

I'd guess alignment problems, very likely rear toe is out too far.

Could be a milion things. Check the tires if they show signs of suspension wear. A worn front lower vall joint will make the car dance when you are on the highway and hit a pothole/bump.