Historically I have seen regen limits come in circumstances that are a bit of a surprise. It's highly unlikely that this is an issue. However, when you say "constantly" do you really mean all the time even on a long journey or do just mean at the beginning of each recent drive? If it really is constant and this behaviour doesn't change after a 2 button reset ... and a sleep ... then it would be worth contacting Tesla Service for their assessment. They can access some parameters remotely which can add to their understanding of what may be going on.