Please check with your gynac if you are facing severe sleep issues or body aches. They can suggest safe sleeping postures or pillows. Normal comfortable sleep is fine in early weeks though.
My doctor told me that sleeping on the left side improves blood flow to the placenta. I bought a C-shaped pregnancy pillow and it literally changed my life during those early months.
In my home, everyone told me to sleep only on the left side, but my doctor said in the first trimester you can sleep in any position that makes you comfortable. Just avoid sleeping on your stomach as your belly starts growing.
Be very careful with your posture, but sleep comfort is important too. If you feel any weird cramping or back pain, mention it to your gynac. Otherwise, just use a soft pillow for support.
Actually yaar, first trimester me sleep is so bad because of nausea and fatigue. Honestly, just sleep however you feel comfortable right now. Later on, left side sleeping is best.