I have a 2000 Sonata 4 cylinder model and I've noticed in the last week
or so that there is a very slight, almost imperceptible lurch when
driving along around 50-55 kilometers per hour (I'm Canadian so I don't
use miles in my lingo).

The lurch isn't when its shifting gears, just driving along. As I
mentioned its so slight and it happens so quick that I don't even have
time to glance down at my guages but I don't notice the rpms or speed
changing in these small lurches. I do have my air on all the time and I
tried a couple of times with the air off and for those little
experiments, it didn't happen.

Could the extra load of the air conditioning cause this or is it a
coincidence? Or is this a symptom of a bigger problem. I hope
Hyundaitech can help with this but all other opinions would be welcome.

Thanks