Have taken it in about 5 times last winter and again today, but mechanic can't figure out what's wrong. Only happens when it's been sitting out in cold weather. Shortly after accelerating, it won't shift above 2nd gear. The ABS light comes on and sometimes I lose the spedometer. If I shut off the engine for a few minutes, it starts back up and runs fine. Just very frustrating. Any ideas??? Mechanic replaced some type of sensor last year, but it didn't help. No codes come up, no check engine lights.

Wewlcome to AF.
Speed sensor or speed sensor circuit wiring problem.

For ABS codes you will need a abs capable scanner and test for the code with light on and before turning key off.

Collect all codes abs and engine and post back code no.
MT