"Rough start" is kinda vague, but I had a version of that on mine when it was cool or cold overnight. Long story short, I had one of the heater grid relays quit working. They are located on a common bracket on the driver's side fender well. Follow the leads back from the grids & you'll see them. Make sure both ends of both leads are tight too. Get a tester, lets the grids cycle, & see if you have current on BOTH sides of each relay. I had to replace mine for about $65 at the dealer, couldn't find them anywhere else. I kept the old set as a spare, because one relay was still working, and can be removed from the bracket. It takes both relays working to smooth out a cold start.