I would start with easier possibilities first.  Even if they are not as likely.  
First thing I would do is turn the grill on and let it set for a minute or two before lighting it.  This will tell you if actually lighting the grill is causing the problem or it is just a lack of gas flow after a few seconds.  It may not answer the question, but it is quick and easy and will provide more information.
Then, I would start at the tank itself.  Swap in a new (different) tank and see if that changes anything.  The OPD in the tank could be malfunctioning.  Again, very easy and quick.  After that it is going to get a bit more complicated and you will have to move on to the hose, regulator, manifold, valves and burners