I have a 1999 Subaru Legacy GT wagon, automatic transmission. About two weeks ago it started to do something very strange:

The first time I start it up each day, it drives fine. But the second time I drive it that day (e.g, driving home from work, or leaving the supermarket), it starts up fine, but when I step on the gas, it is very sluggish, until first gear kicks in and then it lurches forward. It does this as it goes to second gear as well. After a few seconds, however, the problem seems to go away, and then it drives fine again until the next day, the second time I drive it.

Does this sound familiar to anyone? Why would it only happen the second time I drive the car each day?