The incident took place on the evening of Monday 11 April.
Officers attended reports of an unattended dark-coloured van on the hard shoulder of the M11 between the Redbridge roundabout and Loughton shortly after 20.00 BST
Once at the scene, officers found a man within the vehicle who required hospital treatment. He was taken to a nearby hospital.
He has now died, and police are treating his death as unexplained.
Officers are now appealing for anyone who noticed any suspicious behaviour on the M11 between the Redbridge roundabout and Loughton between 7.30pm and 8.10pm on Monday 11 April or caught any suspicious behaviour on dashcam to come forward.
If you have any information you can submit a report online or use the ‘Live Chat’ button to speak to an online operator between 7am and 11pm on the Essex Police website.
You can also call 101 quoting incident 1121 of April 11.
