A restless state of mind that wanders away from an object while observing it is a mental state called restlessness (uddhacca). It flies away from the… - Mahasi Sayadaw

One should keep oneself occupied all the time with wholesome deeds such as: learning, teaching, memorizing, reading, scrutinizing, and chanting the Buddhist scriptures; discharging the daily duties of a monk; discussing the Dhamma, only speaking about the Dhamma; giving or listening to Dhamma talks, and practicing asceticism.

Sometimes the mind may wonder about practice itself. For example, the mind may wander off into analyzing whether an object was noted effectly, or sequentially, or vividly. The mind may wander off into thinking about how one is going to note an object. Under these circumstances, insight concentration cannot arise.

Doubt about the fact that insight wholesomeness consists of simply observing the presently arising mental and physical phenomena is also skeptical doubt. This doubt is so subtle that it is rarely detected but is instead mistaken for investigation. This doubt masquerades as analytical knowledge. The commentary on Netti Yuttihāra explains as follows: "Doubt appears in the guise of investigation."