Piezo Electric Vibration sensor

HI guys, please take a look at the picture attached.
My sensor is connected with a 10M resistor for A0 and ground. The input is 5v.
The coding normally runs well and the sensor shows signal only if the vibration is detected.
However, all of a sudden, the output appears to become repeating amplitude when there is not even any vibration trigger the sensor. Should this because of the connection problem?

That is likely a floating input, picking up AC line interference. Fix your connections and consider using a 1 Meg resistor instead.

Third cross-post for this project.

A WeMos D1 min has a 320k load resistor (220k:100k voltage divider) on the analogue input. Bit low for a piezo, and adding 10Meg or 1Meg to that won't make a difference. Leo..