I own a 2000 Forester LT with a little of 200k miles on it. 4 cylinder engine,automatic transmission.  Recently, when I first start the car after it has been sitting for a few hours the At Oil Temp light begins to flash constantly. If I drive it for a short distance or allow it to completely warm up and then turn the car off and back on again the light will stop flashing. However, there is also a lurching motion in the shifting that varies between 1st and 2nd or 2nd and 3rd depending on whether the engine has had a chance to warm up (1st and 2nd when cold, 2nd and 3rd when at temp). A few months ago my dear boyfriend went to change the oil in the car and accidently drained the transmission instead of the oil pan. He realized his mistake before either of us drove it and put new transmission fluid back in but did not change the filter to it. He also dropped the filter in a pan of motor oil before putting it back on the car. That was back in July and the dash light and lurching motion only started in the last
few days. Is it possible that my transmission filter is simply clogged and needs changed or is this a symptom of a larger problem. The lurching motion, after the car is at temp, comes and goes so don't know if it's the transmission itself, the filter or maybe a sensor of some kind.
 

Any insight would be greatly appreciated.

 

The blinking light is the transmission computer telling you something is wrong. You'll need a code reader to find out what it's trying to tell you though. This will give much more insight into the actual problem.

It actually tells you there was an electrical failure in the previous operation cycle.

 

I am slightly confused, can be me not you. Does this have an external can type transmission filter you are talking about dropping in motor oil? I would do a full flush of the transmission, as sometimes that works wonders on subaru transmissions.

 

How does the car behave when turning a tight circle?