Under Scotland’s access rights, you can ‘wild’ camp, but should adhere to the Scottish Outdoor Access Code ad seek permission from the landowner before setting up camp. You can find the code, and what is meant by ‘wild’ camping, by following this link: http://www.outdooraccess-scotland.scot/practical-guide-all/camping.
You can find more information about camping and wild camping on Shetland here: https://www.shetland.org/visit/plan/caravan-camping
Please note that campsites can get booked up quite quickly.
Scotland’s access rights do not include motor vehicles. If public or private land owners restrict or regulate parking on their land, you must comply with this.