Jfick-
I had a choc chip star for nearly 3 years that recently died when my nitrates spiked out of control....
Over the course of his 3 years in my community tank, there were periods of time when he would be motionless in the same spot for HOURS on end, and that was during his healthy days. It was not uncommon.
You did not mention how long you've had this star, but if you've had him for a while and recognize this recent 3-hour inactivity as a markedly different pattern or behavior, then your instincts are better than any thing we can likely offer here other than our own histories...
THAT SAID, here is a more recent history with mine prior to his eventual removal from my tank...
During the high nitrate problem of 6-8 weeks ago, when I felt something was definitely 'off' with my star - he displayed a significantly different pattern from his typical feeding pattern, movement, and behavior - whereby I began to notice inactivity for periods of 16-20 hours! At times, certain he was dead, I would move him slightly and sure enough the suckers were still sucking, his arms still active and he would move. I only took him out (following 2-3 weeks of this increasing type of lethargic symptomology) after fewer suckers were sucking, and the fish began picking at him. Then I discovered a small pencil-eraser sized hole in his side one morning. Despite still clinging to the glass with the minimal amount of suckers in 2 of his 5 legs, I felt it was time..it would have only worsened, and I didn't want to introduce any more problems to a tank condition I was already battling...
Hope this may be helpful to your observations over the next few days/weeks.