I keep getting tricked by this, but I try to remember that subjects don't have a preposition in front of them (eg, 'il momento', not 'allo momento'). This helps me realize that it's the moment (or time) that's coming, not something coming to the moment.
Because "I heard" would be translated as "Ho sentito". "Sentivo" could mean "I was hearing" but since there is no context (... was hearing when?), you can't translate it that way. Whereas "I felt/I was feeling" tells the same thing. Clearer now?