@RoccoBass04
Hope this helps:
Okay, I messed with the lick a couple of times today.
I am a big fan of using multiple approaches to learn the same material in different ways...multi-faceted learning. The first time I practiced on my desk (no bass). I set up a sticky note under my right index finger and a sticky note pad under my left middle finger. For the right thumb I simply struck the desktop. The idea is to get different sounds from the different strokes, just like on the bass. IMHO hearing the different tones is helpful and seems to help cement the pattern.
I focused primarily on the pattern THTPHT, THTPHT and which fingers are used. Left index finger lightly pressing the desktop to simulate the mute. Then I simulated the motion of the lick between right thumb (T), left middle finger (H), and right index finger (P). You could also use right middle finger (P) if you like. I tried it both ways as I use both fingers about equally for plucking.
At first, put some effort into thinking about the motion of your individual fingers and try to integrate the different motions into a single stream of consciousness, rather than thinking of it as totally separate events. This basically means you think of two things happening at once rather than trying to keep it all separate. I see sort of a linkage between the right thumb and the left middle finger. One goes down and the other goes up...like the ends of a see saw. So it can be viewed as one event rather than two.
Also observe the pattern as it moves around your finger tips. It reminds me of waves bounce around in a corner. This is different pattern that you can see/visualize and feel. Feel the rhythm of the waves and relax into it. You may perceive this totally different than I do...and that is just fine. However you perceive it, embrace the pattern and make it your own.
As the pattern starts to fall in place you should eventually be able to completely stop thinking about it and just let it continue.
Later I picked up the bass and the lick felt a bit awkward again, partly because the bass was different than the desktop and partly because it had been a few hours since my last practice session.
I started slow and worked it up. Within minutes, the lick started coming together and feeling more natural. It wasn't long until I could turn on my Boss Dr Beat and play along for an extended time with 1/4 note and triplet 8th note pulses. I don't remember if I had the beat set to 124 or 128bpm, but it felt pretty relaxed and I think I can play it a bit faster without the lick falling apart.
One minor problem is the harmonic wants to ring from the pluck. This is not necessarily a bad thing as this could be intended (or not), but controlling it requires additional muting...which is something else to think about.
I tried using my left hand pinkie and also my right palm. IMHO, the palm requires more attention and finesse. Also using the palm changes the angle of the right hand strokes, which feels a bit less natural to me. Using the pinkie on the G string was a bit confounding at first, but the difficulty did not last long. I am still not certain which would be best in the long term.
I am not getting any clenching in my shoulder. However, I have an idea of what you may be experiencing. Doing this lick involves pushing down with the right palm and forearm. This is done for muting purposes and to stabilize the bass. So over an extended time, the effort could become slightly fatiguing, although I do not find it problematic.
I am not to the point where I feel this lick is entirely internalized. Whenever I begin to practice the pattern, I still have to start slow and think about it. But I am easing into it quicker and quicker. It won't be long until I can just do it randomly whenever I feel like it.
Hint: Starting on the pickup note may help with the double T. I.E. to practice the pattern, hear the triplets in your head and then start like this: T|THTPHT, THTPHT|THTPHT, THTPHT|THTPHT, THTPHT| Also, imagine an accent on the downbeat T. If you really want to get comfortable, try every possible starting point.