That's not a common thing experienced with natural testosterone boosters.
But the category of natural testosterone boosters range from great products to absolutely ridiculously underdosed prop blends; so its too broad to really give an overall answer.
I definitely don't think with most quality ones that it would be elevated DHT levels.
It could be that you're sensitive to a certain ingredient or in a rare case, you could be someone who elevating test levels itself causes an increase in heart rate. Very very rare, but medically it does happen (but I doubt this is the case).
I don't discuss products by name openly on the forum, but if you want to pm me a list of the ones you've tried and experienced this with, I'll be glad to try to help you figure it out. (I may not be back on here today, so if you pm me today and I don't reply until tomorrow, not ignoring you).