Did you find out why you are tensing your neck? My 6 year old daughter has been doing this constantly. She says it tickles and she clenches her lower jaw and neck.
I do something very similar, except I make a sound in my throat when I do it. It is driving me crazy. I try to control it when I am around people but just discovered that my co worker hears me doing it. By the end of the day my throat is exhausted.
I can only think that maybe it is a habit that I need to break and nothing more.
Let me rephrase that. Sometimes, we have a tendency to allow our neck and head to slump forward. Even though you may think your head is level, the whole structure (neck and head) are slumped forward, make sure the neck and shoulders are pulled back and in line with each other. Look in the mirror.
Make sure you are holding your neck back, level with the shoulders. Leaning the neck.head forward will cause some nasty tension over time.
Sometimes side effects from medications can cause your throat to tighten up exactly like it's doing, so review all the drugs you are on. And you need to be taking something for your sinuses, if you aren't already, and ALSO you should drink about six glasses of water daily as a habit, to prevent your throat from drying out. On your thyroid, sometimes it can swell up and get worse, even tho your readings were normal last time, so visit your endocrinologist about that possibility. As for the TMJ, it is possible it has really gone out of the socket and is jerking your jaw and neck muscles and nerves rather significantly, which a dentist or an ear nose throat ENT doc can look into at how that's doing.
The only other thing I can think of, altho I do think it's side effects from some drug you're taking (even over-the-counter or herbal supplements), is you need to perhaps have a friend or relative or a professional massage therapist rub out your shoulder muscles really well for a few times. Stress lands in the shoulders. Also, to help your throat relax, practice deep breathing techniques, which is basically taking in a real deep breath, blowing it out, then breathe normally a few times, then breathe in deep a second time, and continue with this ten times. Then just drop your jaw down and let it completely relax, rub where the jaw joins the head to keep it dropped down, relax your eyelids, and just focus on maybe some soft music or light bouncing off a shiny object in a window, and do that for as long as you can stand it (it's hard to relax the jaw like that).
Let us know how things go for you on this issue.