I have an issue with my Ultra1 that is the reverse. If I leave mine off
for a long time (a few months), I have the same issue (beeps from the
speaker, box won't boot), but if I fire it up every day I have no
issues. .

I went back to the ok prompt and did a probe-scsi-all which showed the
hard drive was offline.
What I did was boot cdrom -s from the the ok prompt and run format. I
guess the probing was enough to bring the disk back online because I
was able to see the disk and mount the partitions.

If doing the boot cdrom -s and format dowsn't work for you my guess
would be a hard drive replacement is in order.

Dean