Test voltage...

When my alternator was going I would occasionally lose my speedo along with the trifecta lights. You said the car sat for a while, maybe the battery went bad over that time and won't hold a full charge, maybe that caused the alternator to work overtime. It's worth a look as checking the voltage is free and takes just a few minutes with the OBC hack.

__________________
Current Bimmer
2004 X5 4.4i Sterling Grey Sport/Premium

Past Bimmers
1991 318I Alpine White
1995 740I Alpine White
1991 525I Schwartz
1998 323IS Scwartz
2004 330CI Cabrio Titanium Silver Metallic
1995 540I Schwartz
2000 Z4 3.0 Titanium Silver
2000 330ci Coupe Titanium Silver