It's hard to imagine myself into a game world.
My imagination in that respect is a bit dim I'm afraid...
Then find yourself games you can immerse yourself in (immersion overall, is key), find books and other media that can do the same. If not that, try to develop your own, ignoring what others would think about it (like my avatar; "Screw physics", or better yet in general, screw realism or being realistic overall); no need to publish anything (unless you truly want to), this is purely for yourself. Have fun, and your imagination would soon follow. Ideas and such could be lame in one sense, but then again, another look at it at a later time can always change things.
A good example of that could be like me watching One Piece before I took an interest in anime in general (late bloomer there, started in my mid-20s). I found it too silly, and some concepts and characters dumb and inexplicably silly; then I took an interest in anime a fair/far time later, grew up a bit, and re-watched the show again, and this time, also from the beginning. As it turns out, in hindsight, they're reputably badass enough in-universe to get away with being that silly, at least, until Luffy and crew comes in and humbles them one way or another; with or without fighting them. Just as well, when you actually come and think of it, it's like an endless faucet of imagination set to full with these things throughout the series; kinda reminds me of how my mind used to operate, except with a sea pirate theme. Kinda made me wish I was a fan of it when it first came out. But all that aside, use your imagination, no matter how dumb others may think the end result may be.
Who knows, you could live in a One Piece-like universe inside your mind. In a sense, the most recurring world always was like One Piece, except with a space pirate theme, with a hint of Lovecraft, Dr. Seuss, The Far Side, and Calvin & Hobbes in the mix, some Biblical referencing here and there, and the right mix of practical and zeerust styles with some extra-dimensional existential horror for flavor, looking like a bastard child of Star Wars, Star Trek, Lexx, Doctor Who, and Farscape, with a dash of Stargate, Alien, Land of the Lost, Twilight Zone, and Space Dandy, colliding and blending in with Our Earth (via at least my conscious) being relevant in the whole mix one way or another, like Futurama.
In a realm where you are not amongst, nor judged by society, don't be discouraged or scared. You are essentially God here. Go fucking nuts.