I often count the amount of letters in a sentence, phrase, or title. I can usually do it in about a second, I group the letters into fives, fours, or threes to make the process easy.
When I eat snacks like popcorn, chips, or small candies, I eat them in even numbers. Sometimes to avoid that compulsion I just grab a fistful. Kinda getting over that one.
Whenever I visit a friend I immediately scan the wifi for smart home devices. If there's an Alexa or Google Home, it needs to be disconnected or I'm out.
I also do the exact same as
@Relativ9 posted, and I always assumed that was just normal introspection.
I ask friends if they have an inner monologue or are capable of visualizing in their head. I can, and to most people that's normal, but some people can't (and apparently don't know that others can), and I'm always trying to figure out what that's like, and I want to know how it affects one's creativity, critical thinking, introspection, as well as their perception of dreams and memories. The dumbest person I knew lacked an inner monologue as well as the ability to visualize, but he was also English, so he's an unfair example, and a sample size of one isn't of any use.
I remove the cameras and microphones from electronic devices I purchase. I've only left them in my phone, though I keep the... front? back? smaller camera taped over with a LightDim sticker. I've considered purchasing a faraday cage to keep it in at home (I don't text except to organize to meet up with people in person, and I keep it on do not disturb 24/7), but I'll probably buy a PinePhone, in which case I can use a physical toggle to disable hardware I'm not using.
The only app allowed to give me notifications on my phone is Google Voice. I don't pay for service or use a SIM card.
... I'm not confident I'm the only person who does any of these.