Keep in mind that D&D was originally played with large groups. As
@aco175 states, let the players help. One way to do this is to bring back the old-school role of group caller. The players discuss what they are going to do and the caller tells the GM. Whether the players like this depends on the group. For more thespian players who are really into playing a role, it may be unsatisfying. For more tactical players who like to think through situations, it will likely be appreciated.
I think my old Toast Masters experience comes into play here. In addition to playing their character, give the players a role in running the game. It will keep them more engaged when it is not their turn. Some roles I've delegated to players to make my life easier and to help them keep more active, includes:
1. Initiative tracker. If you are not using a VTT or other digital tool, have players take turns tracking initiative during battles.
2. Time keeper. If time is important in your game, for random encounters, deadlines, etc. Let one of the players track it. I have a time tracking chart printed and laminated that you place six-side dice of different colors on to track rounds, minutes, and hours, and a wet-erase pen to mark off days and weeks. It gives the player a cool new thing to play with rather than using a spreadsheet or notes on paper.
3. Party inventory / XP. Have someone take responsibility for recording collected treasure and XP
4. Note taker. Not for everyone or every group. Many people prefer to take their own notes, many people hate taking any notes. But sometimes there is a player who is good at and enjoys taking notes.
5. DJ. It can be fun to play background music. Let the player control the playlist, Syrinscape, or whatever you are using.
6. Drawing battlemaps, placing terrain. For in-person groups, for more simple encounters, I'll just have the players draw out the battlemap and place the terrain. I just give some general guidelines. This is one thing I miss now that I'm running my game in VTTs and am running a massive megadungeon where everything is all mapped out.
7. Inspiration tracker. One thing I've played with that works better for me than RAW is to have an inspiration pool. The party can have inspiration up to the number of players. It only lasts for the session. To earn inspiration they have to either play a character trait in a manner that may be otherwise against their interests but which benefits the party. Or they take a big risk, or just do something funny/cool that is related to a bond/flaw/ideal. The inspiration pool is tracked and as they use it, it is removed from the party pool. This encourages risk taking early in the session and helps kick people into their roles, while given a thematic bonus later in the session when they are lower on resources. It also prevents hoarding of inspiration by players are are worried that if they use their one shot of inspiration, they won't have it if they need it later.