two (or more) trys to start/low power

[Alberta Luthier]

So When I crank over my 83 300CD it often won't start on the first try. I let the glow plugs heat then crank and it doesn't usually start on the first try. Then off and back on immediately and it starts right away(without waiting for more glow .... like it isn't getting power to the spark plugs haha but of course it doesn't need power.
Sometimes especially when it is already warmed up, and after cranking it for a bit it does start on the first try... but then it barely runs, it idles down to around 500 rpm and floored... has half the power of a 240 .... or less. -like 5 minutes to get around the block!! Then I shut it off and restart and after one or more (lately much more) attempts it fires up like it finally got fuel and goes very very well.
I have searched a lot and not found anyone with the exact problem.
Could the fuel shut off thingy be sortta stuck???? And just where and how do I get to the fuel shut off thingy if that is it.
Please help my Family is making fun of my car