I'm hearing a grinding in the engine when starting in cold weather on 2004 Toyota Camry

In cold weather or when the car hasn't been started in a few days, on starting, I hear a metallic grinding in the engine. Today when it happened I smelled a burning or hot smell coming through the vents. The car runs great otherwise. The dealer hasn't been able to locate the problem, but the car is usually warm when they see it.
Thanks for any help

Asked by for the 2004 Toyota Camry
Try leaving the car overnight at the dealer so they can cold start it in the morning. The noise could be inside the engine or outside the engine. If it's inside the engine the only way you can be sure its not damaging the engine is to check the oil on the dip stick for a silver glitter look to it. If you don't see anything check the oil in a drain pan when you perform your next oil change for the same silver glitter look to it. If it's really cold you may want to consider using a thinner weight oil like 5W-30 if you are'nt already doing so.