|If a separate mouse - and the type that has a small ball... then it may be it needs its privates cleaning...|
The little ball would benefit from a warm soap and water wash. The innards to have the little rollers cleaned too; remove accumulated "stuff" that wraps itself arounf those rollers...
If more current laser style... It may be it's developed internal faults.
Have you tried with another rodent (presuming the problem as posted is re' an external rodent/mouse)?