Traffic was initially stopped on the southbound carriageway between Junction 15, Stoke, and 14 for Stafford while emergency services dealt with the blaze.
Pictures showed the HGV, a car transporter, on the hard shoulder with the cab in hedges, after the fire was extinguished and two lanes reopened.
At its peak the queue of traffic stretched back for nine miles; at midday National Highways said there was five miles of congestion adding 35 minutes onto journey times.
Elsewhere a man has died and two others have been injured in a two-car crash on the M42.
West Midlands Ambulance Service was called to the incident near Junction 9 at 3.36am and sent three ambulances, three paramedic officers and a trauma doctor and critical care paramedic to the scene.
A spokeswoman said a passenger from one of the cars was found in a critical condition and given advanced live support, but nothing could be done to save him and he was confirmed dead at the scene.
“The driver of the first car had sustained serious injuries. He received treatment from ambulance staff before being conveyed to Queen Elizabeth Hospital under blue light conditions," the added.
“The driver of the second car had sustained non-life threatening injuries. He received treatment at the scene before being conveyed to Heartlands Hospital for further assessment.”