If this is the case, you're probably overwatering. Unfortunately, overwatering is a more serious problem than underwatering, as roots tend to rot in soggy soil. There's also a chance your plant is in a spot that’s too hot or sunny, which many houseplants can’t handle. If the roots are poking out of the pot, your plant is pot-bound and has outgrown its vessel, which can also cause wilting. Lastly, if your plant has been outside in summer, vine weevil grubs (white, 1-centimeter-long, comma-shaped insects) may have eaten the roots.
How to save it: If you’ve underwatered, plunge the pot into a bowl of tepid water for half an hour. If you’ve overwatered and the compost is very soggy, dry it out by wrapping the root in kitchen paper to absorb excess moisture. If the roots have turned brown and mushy, you won’t be able to save your plant. Move your plant to a cooler, less sunny spot if needed, and if it’s pot-bound, replant it into a larger pot.