The short answer
Yes. Treks of two to four days run at both Erg Chebbi and Erg Chigaga, taking you away from the camps into quieter parts of the dunes, with nights in simple bivouacs. Chigaga is the more adventurous choice. A trek needs planning in advance, a reasonable level of fitness, and something to protect your legs from the saddle.
In more detail
Most visitors ride a camel only to and from a camp. A multi-day trek is a different thing: you ride and walk for several hours a day with a camel guide, camp where the day ends, and cover ground that day visitors never see. Our camel guide describes treks of two to four days at both great ergs.
Comfort matters on day two and three. The rolling gait is easy for an hour; over several hours it tells on the inner thighs. Our guide suggests padded cycling shorts under loose trousers. Many trekkers walk alongside the camel for part of each day, which helps.
Season matters even more. October to April is the time for it; outside those months the heat makes a trek an endurance test. Add the drive from Marrakech, and a camel trek needs at least five or six days in all. Tell us early and we will plan the camp, the guide and the route.