Is one sinful for thinking of missing the Maghrib prayer with the 'Isha congregation out of shyness, upon the entry of the 'Isha prayer time?

Thinking about a sin does not hold a person accountable if they do not act upon it or speak of it. Whoever misses a prayer due to sleep is excused. It is permissible for someone who wishes to pray 'Isha' with the congregation and then pray Maghrib afterward, according to those who do not stipulate the order between the two prayers. There is no sin upon him if he fears being misunderstood or causing disagreement. We warn against obsessive thoughts (waswasah) that lead to extremism and excessive rigidity.