If Teddy always does this at the same wall, it's possible he may see minuscule insects on the wall. If he does it on other walls, insects or even shadows are possible, that attract him and peak his interest. It's also possible that he may hear something or smell something on or near this wall.
There are certain medical issues that may cause a cat to start into space or stare at a wall and one is feline hyperesthesia. Typically with this condition, a cat's skin will ripple or twitch on her back and she will take off running through the house for no discernible reason. This is a neurological condition, so if more has to be looked into, your regular vet might refer you to a veterinary neurology specialist. Here is more information:
I hope all will be well with Teddy!
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