As someone who went from 430 ng/dl to 1024 ng/dl naturally in about two years time (from age 23 to 25) the only thing I can say is don't jump to too many conclusions here.
- Your testosterone should be naturally high if you're below 30 (and male)
- If not, something is wrong and you need to fix it (start with blood work, check your diet, move)
- If you testosterone is in the normal ranges (blood work recommends between 600 and 1200, which is ridiculous), you'll feel good 80-90% of the time
- the 10-20% are probably psychological worries that you might have, start meditating
- I didn't get huge muscles or less body fat with more testosterone (huge myth that I thought would change for me)
- TRT is used heavily in pro-sports (look for UFC fighters and bodybuilders, they have the most experience, since a lot of them are doing it)
- TRT is a problem if you keep going for too long, because your body just doesn't produce testosterone as it used to, because it expects it from the outside, so below 35 or rather below 40 year olds: don't sign up for this too quickly.
- Cold showers/baths do work, but probably not for increasing your testosterone, still, do it from time to time :)
- Intermittent Fasting helps immensely with boosting your testosterone naturally.
I can provide more info or details/specifics if wanted/needed.