erroneous measurements of my heart beat

Hello!

Often my watch gives erroneous measurements of my heart beat.

This happens typically when I put the watch on when I get out of bed in the morning. The watch says initially that my heart is beating at over 160 or 170 bpm. Then it reverts to a more realistic figure (for me).

The erroneous measurements last generally for about 10 - 20 minutes but sometimes longer.

If I keep the watch on during the night this does not happen when I get out of bed.

The erroneous measurements do not happen at any other time during the day, even if I leave the watch to be recharged.

Have other users experienced similar erroneous measurements?