yesterday i drove my xj for about 40 minutes straight on and off highways but most of it was highway, when i got home i shut it off then 10 minutes later had to go to store so i went to start it but it didnt turn over and sounded really rough. i tried again and it started but it still was insanely rough. i let it sit for a minute while giving it gas then drove away and it was fine. this seems to only happen when i drive for a while and when i go to start it at around 210 degrees, any idea what is happening? PLEASE HELP