Yes, feeling disengaged at work is extremely common. Surveys consistently find that most employees are not actively engaged in their jobs. So if you feel flat about work, you are in the majority, not the exception. The more useful question is whether yours is temporary or a sign of something that needs changing.
Normal, temporary disengagement
Everyone has stretches where work feels dull: a boring project phase, a tiring period after a big push, a January slump. This kind of disengagement passes on its own once conditions change. It is worth riding out rather than overreacting to.
Disengagement that is trying to tell you something
Persistent disengagement is different. If you have felt disconnected for months, dread most mornings, and cannot point to a temporary cause, that is a signal worth taking seriously. It usually means one of a few things: you have outgrown the role, the environment has become unhealthy, or the work no longer fits who you are becoming.
How to tell them apart
Ask yourself whether anything would re-engage you. If a new challenge, a change of team, or more responsibility would light you back up, the problem is fixable where you are. If you honestly cannot imagine anything about this job pulling you back, the disengagement is pointing you toward a bigger change.
What to do either way
For temporary dips, protect your energy and wait it out while making small improvements to your week. For deeper disengagement, treat it as information. It often marks the point where people invest in new skills or qualifications to move toward work that engages them again. Building capability is one of the more reliable routes out of a role you have outgrown.
Feeling disengaged is normal and human. The mistake is ignoring it when it stops being temporary. Work out which kind you have, then respond to that.
If low mood at work is affecting your health, sleep or daily life more broadly, it is worth speaking to your GP or a qualified professional.