I have a 1988 GTA Trans Am, 5 speed with 305 TPI

I have a really weird issue, i will be driving and go to pick up speed but the car wont go, its still running, if i stop it idles fine, just drags and picks up speed really slow

Now if i shut the car off and start it up it is all back to normal

This originaly only happened if i drove around for a while, the other day it happened as soon as i got on the highway, car was running only 5 minutes

any ideas?