Play a C Major scale. Then sing the C major scale. Do not sing one note at a time and wait a whole lot of time to sing the next note. Each note is a clue to the next one and when you try to sing them alone you are going to feel lost. Even if you sing to match a tone, I think you are better off singing intervals. And to try and pull the tone out of your head without a context is hard. That's why people ask for starting notes when they sing.
THe problem you are having begins with not just matching a tone but being able to hear the intervals, the distance between notes. So find a short tune, or scale, with fixed relationship that are very very very familiar to you. Also singing so quietly is not helping you. Just sing at a decent level even if the note is wrong. Commit to the sound you are going to make even if it's wrong.
If you can't sing a scale, can you sing a simple nursery rhyme? Or a television jingle? Or two note intervals?