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..