It happened around 5:30 a.m. in the 4900 block of Tidwell Road at Lockwood Drive.
Houston firefighters were called to the area as CPR was being performed on the victim.
Houston police say the victim woke up at a motel and was behaving erratically.
The man allegedly assaulted his girlfriend, then walked into the road and started approaching cars, police say. He was struck shortly after.
Police say the driver who struck the pedestrian originally left the scene, but later returned to talk to authorities.
The victim's girlfriend was transported to the hospital to evaluate her assault injuries, which police say are minor.
No charges have been filed at this time.