LOC intercept is just that. Do not descent on G/S until cleared.
Terrain restrictions below may require an initial higher than G/S stepped down descent and capture the G/S from above (e.g. ALC runway 10, when completing the procedural turn flying a large DME arc, mandatory speed 180kts, vertical profile is high until ~10nm final, G/S signal may scallop due terrain until then providing "false" G/S signals).
Airspace restrictions below may require an initial higher than G/S descent to clear airspace below the G/S reserved for other aircraft or airports (e.g. BHX runway 33 when arriving from South-East [London] requires overflying CVT, especially busy in VFR weekends).
ATC may have VFR/IFR traffic below you, again causing, sometimes this traffic is not carrying a transponder with altitude information thus you (operating crew) cannot see them necessarily. However ATC may be aware and thus not (yet) allowing you to descent on G/S until clear of traffic.
All respondents are so far correct: do not, unless "Cleared for Approach".