Full disclosure: There have been a lot of changes in both the environment and the car in the past few months, so it's very hard to determine whether this is a new development or something that's maybe been there and become magnified. The issue is also not perfectly repeatable, so it's hard to pin down.
The symptom is right at the startup of the car. Turn the key, engine cranks, and as soon as it catches the revs jump up, only instead of running up to 1300 or so, they stay put at a point between 600 and 800. Those numbers are off of the tachometer, which jumps to the engine speed as soon as the key is released, and confirmed based on the sound of the engine. The idle then sits there for between 2 and 4 seconds before jumping up to the usual 1300 and resuming the normal idle. This only happens when A)the car is in direct sunlight, and B)the car was driven at very slow speeds or idled before being shut off. It's happened three times in the past two weeks, and those are the only consistencies I can find. Car could've been off for 10 minutes or 2 days, doesn't make a difference.
Just did the Timing Belt: did I mess something up? seems to run great the rest of the time
All summer the car was driven every day, now it's 3-4 times a week, maybe the battery is weak(last replaced by dealer in 2012)?
2 months ago fixed A/C valve and recharged A/C system, the first time the A/C was on and I blamed the valve for catching early, but the third time the A/C was off at the end of the last drive, which seems to eliminate that.
Replaced plugs at beginning of the summer, again has run flawlessly all summer so those seem hard to blame
Car has seemed to start rough during cold weather for the past 3ish years, but drove fine the rest of the time so never properly diagnosed that
My drives are usually between 20-30 minutes with a mix of freeway and rural roads, don't see an issue there
Forum searches turn up similar problems with 1.8Ts due to MAF connections, but I haven't seen anything on the 2.0Ts, and mine seems fine.