After doing my Asanas, Pranayama and Meditation, when I proceed to lay down to Rest, my legs automatically cross and I automatically start doing moolabandha.
It sounds like some automatic yoga is happening. You have subconsciously realised you're onto something with your yoga practices and there's the drive to get to results quickly! The impulse to press on the perineum you describe in another post is just another manifestation of the same drive.
It is a sign the practices are working. Be careful about doing too much. Automatic yoga adds to the effect of your other practices, so I will repeat my advice to give some thought to self-pacing.
Automatic yoga impulses are not outside your control. If you decide it's best to check them for the sake of self-pacing, gently direct your awareness towards these impulses without encouraging them and you will find they subside.