I’d suggest you take a few steps back and get to know Arduino, Nodemcu and digital pin and relay behaviour first - then add Blynk/wifi on top of that.
Different pins have different behaviour on startup, some are pulled HIGH, some LOW, some momentary, some indeterminant etc . . . you need to research you board and see what is happening with the pins you are using in your sketch. Then you have a number of choice:
- Modify your sketch to accommodate the startup state for each pin;
- Select different pins that fit your need better, or
- Set the state of the pins (digitalWrite) on startup - this may work but you may still see erratic behaviour temporarily during startup.
You need to understand your hardware and adjust your sketch accordingly.