Accelerometers are really sensitive, which is great for sleep tracking. Usually what you see when you leave the phone on the table is immediately dwarfed when you make a more significant movement. Just leave the phone on the table for a while and you will see a dramatic spike, but then move the phone and you will see that all the development is really tiny compared to the new peak.
This is a companion discussion topic for the original entry at https://sleep.urbandroid.org/docs/faqs/dont_trust_results.html