
D,
Don't suppose a nice friend forgot and left his egg salad sandwhich laying around that welder after lunch was over?
I think I would lock out / tag out that machine and get a peek inside to see if you notice something obvious, like wiring insulation or contactor coil that is starting to get hotter than it should. Don't forget to check the polarity lugs where your cabling is attached to see if it is loose and causing it to over heat the insulation. Something is not right and if left unattended may end up costing you some down time. I'm not a service tech, but some that monitor the forum know a great deal about the machines and their inner workings. But my guess is something isn't right.
Post your make and model and some should be able to give you some direction as what to look for and when it is time to call in a service tech.
Good Luck,
John Wright