P0300 Random/Multiple Cylinder Misfire on 2000 GMC Sierra - Check Engine Light at 60-70 MPH

My 2000 GMC Sierra shows a check engine light specifically when driving between 60 to 70 miles per hour. The light extinguishes when I drive at lower speeds. A code reader confirms P0300: Random/Multiple Cylinder Misfire Detected. No other diagnostic trouble codes are present. Freeze frame data: - Calculated Load: 8% - Coolant Temperature: 194°F - Short Term Fuel Trim (Bank One): -4.68% | Long Term Fuel Trim (Bank One): 3.12% - Short Term Fuel Trim (Bank Two): 3.12% | Long Term Fuel Trim (Bank Two): 0.00% - Intake Manifold Absolute Pressure: 9.4 in.hg - Engine RPM: 1921 rpm - Vehicle Speed: 63 MPH - Air Flow Rate (MAF): 2.59 lb/min - Absolute Throttle Position: 12% The misfire appears to occur under specific speed conditions and resolves at lower speeds. I'm seeking advice on potential causes or troubleshooting steps for this P0300 code in a 2000 GMC Sierra. Any insights would be greatly appreciated.