involuntaries start,but..........

It is normal. Keep reading, keep relaxing, keep breathing, and pay attention to what you are feeling. If you're getting to this point, you are feeling the right things. 

If you're feeling arousal and elevated heart rate, try to relax every muscle in your body and pay attention to the pulsing feeling through your body out to your toes and tips of your fingers.

Sorry, I keep skipping the obvious-- as you're experiencing the pulsing of your heart, you are in a somewhat heightened state of awareness of what you are feeling, picture all the pulsing waves radiating out from your prostate/pelvic center/pleasure center/whatever, it starts there. It reverberates there. 

The mind is so fascinating. 

Posted by: @tanjatanja0001

in the past I had several involuntary contractions, which led to the acceleration of the pulse then erection, but then everything disappeared at once! (very frustrating)...

The frustration you are experiencing is a very common phenomenon with many Aneros users. The Aneros experience is not a race or competition but a learning journey without an end point. Frustration is the result of expectations not being met, when you start dropping your expectations I suspect your frustrations will abate with them. You may need to accept the fact that your body may never produce the kind of sensations you want or 'expect' to happen.

Posted by: @tanjatanja0001

now I managed to have it again involuntaries contraction, which lasts 5 to 10 minutes.....but this time I feel no pleasure, no accelerated pulse, no erection!

It seems to me this is indicative of some cognitive dissonance. Your body is obviously responding but your mind is establishing some kind of roadblock. This is a continuation of the problems you previously expressed in the thread i give up...... Erections come and go, some men get them often some don't, this is completely normal.

Posted by: @tanjatanja0001

another thing- I've never had precum leaks, this is normal?

Yes, this is quite normal for some men, including myself. If you are 'expecting' some you are just setting yourself up for continued frustration, just let that thought go. This is related to the issue discussed in the thread "Just Let Go !".

Posted by: @tanjatanja0001

I don't know what to do next.....

@Regal13 gave you some good advice above and I think you need to start examining your own psyche to resolve the apparent dissonance in your mind.

Good Vibes to You!

Sounds like your the rabbit in the headlights. When things get going and they are going from what you’ve described,your ‘eyes’ go wide and your mind is super alert with questions such as is this it? What do I do now? What should I be feeelinh? Am I doing everything right? Just to enjoy what’s happening,the pulses,the erections and contractions. Try to switch off as much as possible.