One thing that may help.

Try forcing your breathing.

As a jogger, I learned that it was really important at times - particularly right at the first of a run and/or before going up a big hill, etc.

Force breathing out - really push it out - As in making a shout on the exhale.

Then after ten or so breaths start sucking in also.

Then keep a measured tempo - heavy breathing, basically a military double time cadence - you've heard them shout them out. You will normally breath in somewhat - but you will not normally force the air all the way out. Doing so, increases oxygen supply to your system primarily to your muscles.

My theory is - early on, your blood stream and system are behind the curve on supplying oxygen to your muscles - this is what makes it tough during the early part - When you smooth out, your system is supplying enough oxygen to your muscles.

When a runner "hits a wall" it is usually that he/she has entered an oxygen deficit situation. No way to win on this one. Have to stop and recover. However, if you force your breathing - you won't hit that wall -

I'm talking recreational running here, not olympic marathon runners, they may well tell you different.

I'm 65, and this system is what has made jogging roughly fifteen miles a week work for me.

Biking - not exactly the same, but in some ways this has helped me a lot - I will start breathing deeper before a grade - and as I go up, pushing harder - I breath harder and force it - and have no problems with the grade. No real hills on my route.

Worth a try, not saying it will solve your issues - but in fact may well make your situation a lot better.