96 Blazer jerking at 50mph
 

I have a 96 Chevy Blazer. 168k miles and no check engine light is on. For a while now whenever i get to 45-50 mph it will jerk. Nothing crazy but the rpms will just bounce around 1.5 until they get to 2. It does it no matter hill, flat surface etc. etc. I read somewhere that it could be a bad ignition coil or something like that. I have no idea where they are located. Or how to check them. If anyone could help, it would be greatly appreciated! Thank you