hi! Welcome to vaping underground....
First off...What is your build? What is your Battery? What is your Mod? It could be a shortage...it could be a dirty button, it could be a bad insulator, it could be a loose post screw, it could be a loose 510 battery screw, it could be a weak spring in your button, it could be a super super low build and the mod is going to get warm after a few hits just from huge current running threw it, it could be a combination of these things, or it could be something else.
You can check your resistance with a multimeter but you need one that carries the decimal to two places at least to check all your leads and need an accurate one (not a super cheap one) to see the difference or the leads are going to read the same unless there is a loose screw or a clipped lead as your ohm checker you screw your atty into to check your resistance of your build. Need a little more info to go on to try and help bud. I am sorry but more info is needed before we can try and help.
