Why dose my 98 k3500 seem to miss when I get up to cruising speed 50-60 mph? on 1998 Chevrolet 3500 Pickup

It don't happen all the time. No codes or malfunction light.

Asked by for the 1998 Chevrolet 3500 Pickup
Gas or Diesel engine sounds like you might have a injector acting up. Maybe just dirty try a good injector cleaner and a tank of premium fuel first. Also get it scanned for codes there may be one that is pending and hasn't set yet.