S10 blazer transmission runs in free
 

So I can start the car as normal, and I can drive away but after 5 minutes it slips tru and can't drive on cause it is like my clutch is in neutral.
It's an automatic transmission.
What should I do?

Get it diagnosed. Sounds like once the transmission fluid warms up, something starts slipping and you loose all forward gears. This could be a bad seal or a clutch problem inside the transmission.