This is a VERY common issue. I have this problem on my Maserati right now it's most likely your igniters not the bulbs even though they probably could use some replacement also. You can get a HID kit from ddmtuning for cheap and they work fine. They come with the HID ballast/igniter AND bulbs for only like $40s.
BMW 2006 M5 - REALLY LOUD
Audi S4 2000 Stage 3 - Dat turbo spool
BMW 2000 3-series
Because race car SOLD
Maserati 2004 M128 GT
- HREs/tint/straight piped SOLD
BMW 2006 M3 - stock - SOLD