There are 2 things tha can cause this:
1.. Your hood or latch is out of adjustment (You will have to adjust it either at the latch or pin. If it is way off, check the whole hood alignment)
2.. Your release machanism is becoming seized. This could be any part of the latch or even the cable.
Most likely it is either or even both of these.
Try some penetrating grease on the latch and pin. You can also try looking at the latch for tell tale signs that the Pin is not striking where it should (i.e. Dents and Scrape Marks)
Cheers,
