Commercial Fixed Wing
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Distraction; Situational Awareness
ATC Issue All Types; Inflight Event / Encounter CFTT / CFIT
General None Reported / Taken
Human Factors; Environment - Non Weather Related; Airspace Structure; Aircraft
We were descending on the JANNY5 Arrival.  At the KOPLE waypoint; we were given 'Direct JANNY at 8;000' by ATC.  We began our descent with Joshua Approach.  Around the JANNY waypoint; we were transferred to SoCal Approach for terminal instructions to Burbank airport. The controller initially gave us a 'descend 7;000' instruction which was followed shortly thereafter with a 'descend 5;000' this descent was well prior to the usual instructions given to Aircraft X from this location.  The crew complied with all instructions from ATC.  We were receiving vectors to intercept the ILS-Z Runway 8 Approach into Burbank.  We became aware that the controller was vectoring us to intercept the localizer between the SILEX and BUDDE intersection.  While approaching from the north at 5;000 ft MSL; we were heading over one of the small mountains northwest of Burbank Airport.  We were vectored near the highest point on that hill which is charted at 3;734 ft.  While going over the hill the aircraft gave us a 'TERRAIN; TERRAIN; PULL UP.' I looked at the RA as the first 'TERRAIN' was enunciated; and saw the RA indicator show around 1;500 feet; then jumped immediately to 2;500 feet.  The warning was only given once by the aircraft.  The PF (Pilot Flying); Captain; reported not seeing any altitude indication on the RA.  We continued the approach and the remainder of the flight was uneventful.  We aren't sure whether it was an erroneous aircraft indication or if ATC may have descended us a little too low for that sector. Clarify with ATC on altitude assigned and whether assigned altitude is appropriate for sector.
Air carrier Captain reported a GPWS alarm while flying into the Burbank airport.