We have a 7 day old kitten - momma cat brought him to the door and left.We got him warm . He had what I think is seizure- his mouth opened up and his toungie came out and his paws went up my his face and he got very stiff- this lasted for about 30 seconds what could be wrong with him

Your ONLY option is to get him to a vet. If it was a seizure, then the vet needs to find out why, and if it can be prevented from happening again. If it wasn't a seizure, then the vet needs to figure out what it was, and if it poses a threat to his health.

Now, before you get mad at me, I know and understand what it's like to not have vet money for an unexpected pet. I also know that if it was a human child, there would be no doubt in anyone's mind that he needed to see a doctor. If you can't afford to pay up front, then call around and try to find a vet that will let you set up a payment plan.