1999 Honda Civic Bucking and a sweet smell

I have a 1999 Honda Civic. A couple of days ago I started the car after it had been sitting for about a week. The car reacted like I had started it with the clutch engaged and bucked a couple of times and again when I released the parking brake. I drove it a little after the bucking stopped and the engine was much louder than usual. There was also a sweet burning smell. I drove around the block and turned off the car, then restarted it an hour later. It started without a problem, the engine sounded normal and the smell was gone. Two days later I again started it up with no problem, and drove it around the block again without incident. Should I be concerned? I'm hesitating to take it in because it only did it once, but fear there may be transmission trouble.