'05 Neon SXT would not start the other day. Had a look around and the spark plugs were covered in oil? Replaced spark plugs and the car started up just fine. Took it out later the same day and car bucked once or twice on my way to the destination. When I went to go home the engine almost didn't want to turn over but it did, however it drove a little rough on the way home.
Separate but possibly related: The coolant reservoir rattled when I turned the car off when I got back home, popped the hood and it looked like the coolant inside was boiling. Only lasted about 15-20 seconds before it stopped. Some coolant did pop out of the overflow spout.

 

Get the battery tested and have your cooling system serviced.