Obvs the first thing is that everyone interprets the word "God" differently. But for myself I'd say I believe that there is
1. a universal consciousness,
2. an energy that works through everything, and
3. that we can tap into both.
Been a slow journey from atheism to this, but mainly based on reading countless first-hand descriptions of enlightenment, mostly related to Kundalini experiences and psychedelic-induced. Reported experiences often fall into such similar categories, sometimes with the same symbology it's either something weirdly evolved in us (for no evolutionary advantage I can see), or some people gain access to deeper levels of reality.
Personal experiences for me that tipped it were:
1. My own Kundalini experiences (not the full-blown transcendental kind yet, but energy surges, meditation phenomena)
2. Receiving remote shaktipat, where energy was projected into me. One of the most surprising was when I was just lying down and a woman 10 miles away sent energy to me for half an hour. It was unmistakable, and wasn't possible she had subconsciously influenced me as she barely spoke to me until after the practice apart from telling me to lie down and relax.
Also, I recently worked out how to 'drop my mind' like Zen practioners talk about. Realised that's the core of concentration-style meditation. Good feelings start to arise on their own.
It's a personal journey (and ultimately the only one that counts), and the mind gets in the way, but each to their own.