WWE legend Kevin Nash is opening up about his son's tragic death ... saying 26-year-old Tristen suffered a seizure in his bedroom and went into cardiac arrest before passing away.
Nash detailed Tristen's final moments on his "Kliq This" podcast on Monday ... revealing they both decided to give up drinking alcohol cold turkey just days earlier.
63-year-old Nash says EMTs were able to revive Tristen as they transported him to the hospital ... where he was hooked up to a breathing tube.