Average duration before ejaculation during masturbation is 20 seconds. is it normal? or signs of premature ejaculation? no history of sexual activity though?

It depends on various factors. There is nothing you should do at this time even if you truly have premature ejaculation. Masturbation is fine but not excessively. The definition of premature ejaculation is only appropriate when you have sexual intercourse.

If accurate, this timing can be called that Premature ejaculation is considered when un controlled ejaculation occurs sooner than or very shortly after penetration- usually less than 2minuts.It can lead tp or can cause anxiety. If not sexually active. Avoid porn, moderate masturbation and you should be OK