Paramedics along with fire crews from Bracknell and Wokingham rushed to Downmill Road, Bracknell, at 4.30pm on Tuesday to rescue the unconscious man from his vehicle.
Gill Hodgetts, head of communications at South Central Ambulance Service, said the 45-year-old was taken to Royal Berkshire Hospital in a critical condition.
He later died in hospital, some time between 5-6pm.
Royal Berkshire Fire and Rescue spokeswoman, Nicole Targett, said crews were informed the driver had experienced a "possible cardiac arrest".
No other vehicles were involved.
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