Is it normal to have night sweats with no fever four days after an appendectomy?

Postop sweats. Walking opens up the base of the lungs and sometimes can cause sweats, an early wounf infection or resolving peritonitis from the appendix can cause sweats for a week or more. Check your temp and call your doctor if fever greater than 100 or wound redness and pain which could happen about post-op day 5.
Talk to your surgeon. May or may not be a sign for concern. Fever may be blunted if taking medications for post-operative pain control that contain anti-inflammatory and / or analgesics (e.g. Ibuprofen, motrin, naprosyn, (naproxen) aspirin, acetaminophen, apap, etc.). Mention this to your surgeon since it could be an early sign of peritonitis.