Go have the code checked. One of the problems that can cause the symptoms you have is the turbine speed sensor (it hides behind the drivers side front wheel.) I had the same symptoms, w/ an intermittent O/D light flashing.
For me it started after I had someone replace the upper O2 sensors. I ended fixing it by checking the wiring around below the coil pack. It had not been properly reattached to the car. (It is housed in a plastic case and bolted to the back of the head below the coil pack.) I think it just put some strain on the wiring when it was just hanging there and caused a weak signal to the brain from the TSS. It got worse in the rain (why I didn't notice it at first).
The TSS is not that hard to replace (search the trans forum.)
Also have the CEL checked, it may be something simple. Autozone will pull the codes for both for free.
