ICDs are entirely compatible with normal sleep. Initially, you may find it uncomfortable to lie on the side of your implant, but most people adjust within a few weeks as the site heals.
If your device is also pacing your heart, you may occasionally be aware of the pacing sensation, particularly when lying still at night. This usually becomes less noticeable over time.
Sleep disturbance is common after cardiac arrest and ICD implantation, and is often related to anxiety, hypervigilance, or adjusting to the reality of having a device rather than the device itself. If sleep problems persist, discuss them with your GP — addressing underlying anxiety or adjusting to your new situation with support can make a significant difference.