Police were initially called to a road crash at an industrial estate in Shepshed, Leicestershire, at about 21:00 GMT on Thursday.
However, officers said it became clear the man's injuries were probably not caused by a crash. The man has not yet been identified.
A 22-year-old man from Coalville has been arrested on suspicion of murder.
Det Insp Simon Shuttleworth, who is leading the investigation, said the victim was found in a silver Ford Focus that had been driven into the industrial estate after 20:00 GMT.
He said two men were also seen running from the scene at about that time.
"It's of critical importance that we trace these two people," he said.
"It's possible the men may have attempted to hitch a lift from a passing motorist."
Gelders Hall Road, where the vehicle was found, remains cordoned off while investigations take place.
The death of a man who was found inside a car that appeared to have hit a wall is being treated as murder.