1997 GMC Sierra after ~20 miles.

If I take highway trips longer than about 15-20 miles and then come to a stop, it truck will jerk when going into 2nd gear. If I let it rest for a few hours, it won't jerk anymore. But then I drive another 15 miles on the highway and stop again, it does the same thing. The 'service engine' light will come on after a couple of these trips in the same day.
any ideas? Shift solenoid?
thanks fellas.