Have some kind of oversensitive nervsys. that makes hr 15 running 5 sec and bloodpressure way higher than normal. should i avoid training or take beta?

Beta? Probably NOT!: Like the rest of our body, primary control is from our mind/brain/emotions; millions orders/sec. Typical resting HR typically ~110 BPM without any orders from brain. But under common acetylcholine output, via vagus nerve to heart, dominating norepinephrine+epinephrine output to heart via spinal cord from brain, resting rates much lower. HR is a response, a symptom/result of mind/brain/feelings.