Mercedes 560SL Hot Start/Driveability

I have a 1989 560SL hat jas 135,000 miles on it and runs wonderfully most of the time. When it is fully hot and I shut it off, then restart it within 20 minutes of shutting it off, it starts fine but you cannot drive it for one minute. If you put it in drive and press the gas before one minute or so, it dies. After a minute or so of idling, you can drive away just fine. If you rev the engine up a bit and hold at 1000 rpm, it (by itself) will rev to about 1500 rpm and then you can let up, idle, put in drive and drive away just fine. This happens 100% of the time. PS: Often when I gas up, I get a burst of positive pressrue release from the gas cap when I open it.