It's an immune modulator. Most people feel worse when they first start, or when they increase the dose. When your immune system really ramps up to fight off an infection you have less energy than normal, flu-ish symptoms etc.
The basic routine is: start, feel worse, wait until you start feeling better (usually takes two weeks max), then bump up the dose again until you reach 4.5mg/day or you don't feel any better after two weeks.
Some people (like me) find that 4.5 is too much. I usually don't take more than 2.5mg/day.
LDN is really good at messing with sleep. I started with 0.125mg/day and slowly titrated to 2.5mg/day over the course of a month. My sleep was disturbed for the entire time. But, the times that I was able to sleep were better than they were without the LDN, so it was worth continuing. Once I hit a stable dose my sleep improved.
That's the endorphin rush. LDN blocks opioid receptors for awhile so the body produces more endorphans than usual. Once the LDN wears off you can get some nice feelings. This only happened for me a few times so there must be some rapid body adaptation to the extra endorphins.
It might disturb your sleep no matter what dose you take. Even 0.125mg/day disturbed my sleep from the first dose. Most people find that once they stay at a dose for at least two weeks then the side effects fade away.
When I reached 4mg/dy I started getting anxiety so I worked my back to 2.5md/day which is my sweet spot for benefits without drawbacks.
If you reduce the dose you might be able to reduce the stimulating effect. It might also be a filler that is causing the stimulation. I read about one person who thought LDN was causing anxiety but then she had some compounded with a different filler and the anxiety disappeared. LDN is water soluble so some people dissolve it in water, then pour it through a moist coffee filter to get rid of the fillers.
Dudley's LDN site has lots of info you may find interesting, including lists of common side effects.