What I am going to say might sound a little off. Can HaShem tell a person that he is Jewish even if there is no known Jewish ancestry? For example I sometimes have a weird feeling that won’t let me go , believing that my maternal grandmother is Jewish. When I believe that everything goes great and I feel blessed when I believe that I am Jewish , for example everything goes amazing ( without requiring me to do anything ) , I feel great , have passion for life and I feel smarter than even. On the other side when I do not believe that , I feel like I am getting punished and actually see my life go from bad to worse. People go against me without any reason , I cannot remember even things that happened a second ago , I cannot focus and whatever I do turns into a disaster. Is it HaShem’s message to me or I am just getting insane ( but I cannot explain why getting punished and not even having the ability to respond to life’s challenges when I reject the Jewish identity)? Also forgot to mention that I feel that my problems feel like forced and there to show me what I am missing. Also another example , I will read an article and believe that I am Jewish and remember everything and then if I read that again but without believing in that feeling I can even remember the title.
Hashem can do anything, however from a practical halachic standpoint if you matenal grandmother isn’t Jewish then you aren’t either. If however you are so attached to Judaism and you are indeed serious about making a serious life changing commitment, then you can consider becoming Jerwish. However if you aren’t very comitted then it isn’t a good idea.