With an automatic, I'd check the neutral safety switch.
Should be able to bypass it for testing.
x2
i had this problem in my 85 but it was a 5 speed and it would do it alot, it came without a starter relay and once i added an aftermarket one it hasnt done it since but i believe your 86 already has a relay for the starter located on the passenger fender well under the hood. might want to check this out after u check the neutral safety switch.
