The perception bobblehead is designed to be obtained extremely early in the game. And technically, you can get the intelligence, agility, and luck bobbleheads without any combat. However, the luck and agility ones, especially the agility one, are still rather difficult to get, so you may very well end up spending more than two hours if you try for them. But they are definitely achievable even in low levels of survival mode, as I have done it. The other three bobbleheads require combat, and are therefore not achievable that early in the game.
For Perception:
It's obtained naturally as you start the main quest in the Museum of Freedom in Concord, in the room where you meet Preston Garvey.
For Intelligence:
If your charisma is low, you may want to grab some charisma gear, charisma boosting items, or the ingredients for grape mentats which can be crafted without any perks (mentats, whiskey, and two hubflowers) as the bobblehead can be obtained with no combat from the Boston Public Library as long as you pass a charisma check at the intercom at the back entrance. However, the charisma check is pretty easy to pass, and Diamond City is nearby, so it's honestly just as easy to savescum it even in survival mode.
For the Agility and Luck Bobbleheads:
Get some rad-x or a hazmat suit ready because the luck bobblehead requires a long swim. You have to get all the way to the Quincy area. If you attempt to run there, it is technically possible while avoiding all combat, but quite difficult, and you may end up dying multiple times while attempting it. Alternatively, you could try swimming all the way from the river north of Diamond City. When you arrive near Quincy, you can sleep safely on some unowned beds in the Atom Cats' garage.
The agility bobblehead is located in the wreck of the FMS Northern Star. It's safest to attempt to get the bobblehead at night. At first it might seem impossible to obtain because the wreck is full of high level enemies, but it's actually possible to cheese your way along the outside of the ship to the bobblehead located on the very tip of the bow.
This will only work while not sneaking, but fortunately, the enemies will ignore you as long as it's sufficiently dark, and you're not terribly unlucky. Go to the starboard side of the ship, where there is a fence alongside. Jump onto a very low section of the fence nearest the gaping hole in the side of the ship, just before a section of the fence made up of a pile of tires. While facing stern-wise, jump to the pile of tires. From there, turn to face the ship (you may need to point a little towards the stern in order to get high enough), and jump as high as you can onto the side of the ship. Carefully strafe until you get to the bow. On the bow, you will be able to jump higher. Carefully jump upwards, while avoiding hitting your head on the jutting beam the bobblehead is perched on, and you'll be able to reach the bobblehead.
The luck bobblehead is just a swim east from the wreck. Just be very careful to avoid the mirelurks on your way into the water. The bobblehead is located in a boat just south of Spectacle Island.