lethargic, unergetic

deficient in alertness or activity; "bullfrogs became lethargic with the first cold nights"

• dazed, foggy, groggy, logy, stuporous — stunned or confused and slow to react (as from blows or drunkenness or exhaustion)
• dreamy, lackadaisical, languid, languorous — lacking spirit or liveliness
• listless — lacking zest or vivacity