I have a '76 Mercedes 450SE. Recently it is having a really hard time starting. When trying to start it backfires and takes a minute or two until it finally starts. When it does start going, it runs really rough for a few minutes and then starts running fine. If I turn off the car and start it again after it has been running a while, it will start just fine. Any ideas?

Choke, ignition advance? Seriously? Do just a little research before posting a "possible solution" to a problem. berts56, start by testing the fuel pressure, it sounds like the engine may be flooding due to a leaking cold start valve, or one or more leaking injectors. Otherwise you could have a leaking check valve at the fuel pump which will cause the engine to loose prime. Keep it simple. Look for any little sign of fuel leak around the pump and filter. Has any work been done on the car recently?

No work had been done recently. I did accidentally run out of gas just before this started happening. Fuel line issues make the most sense since it runs fine one started and warm.

If you ran out of gas try doing some basic maintenance. Fuel, air filter, clean the throttle etc. when gas gets low all the dirt in the tank goes in. do that first...