God is most assuredly a Spirit without any physical attributes.
Genesis 1:1 and 2 NKJV In the beginning God created the heavens and the earth. 2 The earth was without form, and void; and darkness was on the face of the deep. And the Spirit of God was hovering over the face of the waters.
These verses not only tell us that God is the creator of all things material, but that he existed in non-material form, before creation. So let's take a longer look at these Scriptures and see if we can better understand what they tell us.
Verse 1 is key to understanding not only creation, but also many other Scriptures such as John 4:24 cited by Victor Ng in his answer.
In the beginning God created the heavens and the earth. This brings up a question of what does in the beginning mean?
It is quite obvious that in the beginning is in reference to time.
The following is quoted from http://everythingforever.com/einstein.htm
Unfortunately it is very much a reality still today that the works of the really great spirits in science, such as Albert Einstein, Richard Feynman, and Stephen Hawking, and their most fundamental conclusions about the universe, remain unappreciated, even unnoticed by the majority of scientists. These three giants all made very similar conclusions regarding the timelessness of the Universe, yet even today the science of timelessness is overlooked.
Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.
The second statement comes from Einstein's theory of relativity. It is a common belief among these three individuals, (Albert Einstein, Richard Feynman, and Stephen Hawking)that time and motion are interchangeable, and Einstein once stated that if All motion within the Universe could be reversed, time itself would reverse.
Although it was not their intent this theory lends credence to three Omni aspects of God.
If time/motion does exist in a fourth dimension where all events are simultaneous then the Spirit would be able to be omniscient, omnipotent, and omnipresent; as an observer in that fourth dimension, and as it's creator would have the power to reverse time by reversing all motion within the Universe.
The more that Science learns about our environment, the more it validates God as a supreme Spirit.
So let's look at verse 2 and see what it tells us.
The earth was without form, and void; and darkness was on the face of the deep. And the Spirit of God was hovering over the face of the waters.
The earth was without form and void. this indicates that the earth was not solid as we know it today.
and darkness was on the face of the Earth this tells us that there was no light being reflected from it's surface.
And the Spirit of God was hovering over the face of the waters. This tells us that God was there observing his creation as it was in progress.
You might find this video interesting since it shows how verses 1 and 2 probably transpired.
This brings us to a new question How could Moses have imagined the birth of the Earth and most probably the entire Universe?
My personal belief is that he was shown it by an eyewitness (God).
Hope this helps.