Your hard drive may be getting old and taking a little longer to spin up than usual. Try waiting until the hard drive has spun up and then hold down control and the left Amiga and right Amiga buttons on the keyboard. This will do a warm reboot. Since your hard drive is already spinning it should recognize the hard drive.
I had a hard drive that was brand new do this same thing. Installing Kickstart version 3.1 will remedy that as there is a longer spin-up time allowance in the newer Kickstart ROM.
