great mate, thanks for the infoYou can use relay or reed relay on 3V for coil, or if you have more 5V parts you can make 3,3V to 5V converter, see this simple example with MC34063A :
3.3V-5V Voltage Regulator Board
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Circuit : **broken link removed**
Here you can see 3V relays:
If you need 5V just to drive that relay, better is to use 3V relay and solve problem naturally. :wink:
After reset a microcontroller I/O-port is usually in a high impedance state. Thus attached external actuators(transitors/relays etc) will see this floating state and could cause malfunction( more on IO-interfacing and level shifting see https://www.ichaus.biz/wp1_mcu_interface ).
Enjoy your design work!