This sounds a lot like my son from what you have described. We might need more information, because it could be part of a perfectly normal childhood, a phase, or it could be sensory seeking. It sounds a lot like sensory seeking and a talk with your pediatrician might be a good idea.
An evaluation from an Occupational Therapist would be able to tell you for sure, but if he is sensory seeking, then he probably could really benefit from OT. The changes in my just turned 2 year old in the last 3 months have been staggering! I highly recommend getting help if he is sensory seeking.
But, like I said, I don't know what a "normal" baby stage is really like because my were far from normal. So, ask his pediatrician. You might be able to just email or call instead of having to go in. I too have a "tv" baby! Thomas the Train and Super Why are his best friends.
Edited to Add: Like I said, I don't know what a normal 18 month old is, but I do know that my son was not normal at any stage of his life, even at 4 weeks. I do know that 18 months is NOT too young to be concerned and diagnosed with anything. My pediatrician had my son in therapies before he was a year, and started speech at 15 months, and sent him for OT and an Autism screening at 18 months. So, if YOU are concerned, then you really should talk to your son's doctor!