RHR increase on TRT - while this is not a common complaint, it is known to occur. While the phenomenon has not been evaluated extensively, a common theory is that increased viscosity (thickness) of the blood may be a cause. If you haven’t already, you should have your doctor check your hematocrit to see if this is true in your case. Another theory is that on TRT, your testicular function shuts down, and your body recognizes that. So it ramps up your adrenal gland production of testosterone (yes, your adrenal glands also produce testosterone, not just your testicles). Because the adrenal glands also produce adrenaline, the increased adrenal activity releases more adrenaline, raising your heart rate. "

It is possible that you are dealing with something similar to this.

There is also the chance that you may be able to modify your schedule to increase your dose while avoiding this side effect by limiting your T spike. I am making the assumption that you do twice weekly injections. If you're not already, that would be a great place to start.

If you are, you could try to switching to every other day or daily injections. Since you feel it at first then it trails off, and is responsive to your dose size, it is reasonable to assume that at a certain spike you have this negative symptom. Even if you increase your overall weekly dose, if you can spread it out more and avoid that negative spike threshold, that may prove to be a great alternative.

We have men on every other day or daily injects for the purposes of better controlling E2 without wanting to use an AI, it tends to work great for them on the same principle.