The Prophet (ﷺ) would place his right hand under his cheek when about to sleep and supplicate:

اَللَّهُمَّ قِنِي عَذَابَكَ يَوْمَ تَبْعَثُ عِبَادَكَ

Allaahumma qinee 'adhaabaka yawma tab'athu 'ibaadak

O Allah, protect me from Your punishment on the day Your servants are resurrected.

Reference: Sahih (Albani). At-Tirmizi: 3398