Riding with Death (1976)

The ever-so mellow Agent Sam Casey is in a satellite explosion and the radiation turns him invisible. He gets a watch that keeps him visible, and he can use it to switch from visible to invisible. He is given two assignments - The first is to transport a chemical, Tripolydine, purported to be the most efficient fuel. After the cover is blown on that, and Casey uncovers and stops the Tripolydine fraud, he must then stop terrorist Robert Denby from blowing up race cars.