Hello
If the issue is intermittent, it is usually hardware related, such as a bad connection.
However, let's ensure that everything on the software side is properly done first.
Download and install the touchpad driver for this model from Lenovo and see if it helps.
Also make sure you have the latest BIOS - updating BIOS can sometimes trigger the asking of the BitLocker key. IF your BitLocker is enabled, make sure you have the key first.
If the symptoms don't improve after that, you will have to consider a hardware issue; either contact Lenovo or a local repair.
Note: These are not Microsoft websites/URLs, but they are the official OEM/manufacturer sites.