Hard to start 380SEL when hot at times? HELP!

I have a hard start situation in which I cannot figure out what is causing it. This is what the car does. When started cold it cranks and runs without a hitch. Run it until it get's to normal temp and let it set a while and it wil spin and spin and gradually catch up and go. When it finally starts the engine shakes badly and misses for about five to ten seconds then clears up and runs fine. If the car only sits for a few minutes maybe up to five minutes it starts without any problem. The car has 205,000 miles on it and is in great condition. I love this old car and plan to keep it a long time but it's starting to show it's age on mechanical problems. This problem started a short time ago all of a sudden. It seems to me that it is running very rich when it does this but I can't smell the richness if it is. Maybe it is a very lean condition? By the way...... the left cylinder head has started leaking oil from the back of it. THinking of replacing the head gasket but have heard terror stories of the head bolt threads stripping. Should this be a problem that I may face or is this more common on engines that have been run very hot. My engine has never been ran hot. Any info would be helpfull.