Weird burning smell coming from engine

Could be a number of things....something as simple as motor oil or coolant getting spilled on the exhaust can cause a smell when the car is running.

It's good you don't have a check-engine light.....do you get any black dust on your finger when you rub it inside the tailpipe? (If it's burning oil, it will be black.) Do you see any smoke blowing out of the tailpipe when you accelerate at lights? (White or blue or gray or black smoke?)

I'd carry a good light and if I smell anything I'd pull over, pop the hood, and look all around for the source.

 

I would begin with an inspection of the exhaust system. The scenario is plastic garbage from the road lofted and applied to hot exhaust components.

 

Just changed spark plugs.....that's always a clue to why suddenly something is different. If you didn't use OEM parts from the dealership or reputable seller, you most likely bought fake parts that can cause issues, like the burning smell. Did you replace the coils too?

 

Anything untoward prompt the spark plug change, or it was just time? What's the miles on it btw?

I concur with @JC91006: a recent maintenance is a possible cause of new symptom.

 

The source of a smell can be deceiving.... I thought I smelled electric burning from engine compartment once and it turned out to be a battery pack behind back seat.