Cutting off then trouble starting

2001 Work horse.
6.5l cuts out while running then difficult to start, wait 10 min then it cranks up again. When attempting to start it starts clicking, gauges jumping
Checked battery terminals they are secured.
Any Ideas?
Thanks

Sounds like it's definitely a connection problem, or failing batteries. Clicking of the starter solenoid is loss of power under load. Jumping gages suggest it's more likely a breaking connection. Recheck the battery terminals. Remove and clean them, even if they are already tight (usual suspect). They can be corroded under the insulation, which will require replacing the cables. Check the grounds to engine and chassis, and main battery power lug at the starter solenoid. One good and one bad battery will cause them both bad eventually, and can cause the issue you are reporting. Batteries that aren't relatively new should be replaced in pairs, or the cycle will repeat.

Failing ignition switch
A worn out ignition switch can do this nasty trick

As Maverick said
Check batteries/grounds at block.
Check voltages with VOM at both batteries separately.
With vehicle running....check both batteries for voltage.
The RH battery feeds the starter.....
The LH battery connects to the alternator..
Cross over cable ties the two together
One messed up ground can foul the entire system.

With the engine running you should see 14 volts at each battery.
Check across the battery terminals.....

A failed ground will cause all manner of bad stuff.

If these check out good....replace the ignition switch.

I have seen these switches fail on more than one rig.....
They are a linear type slide switch.....they wear out.

Good luck

Had the switch go on my 98 K3500 it would shut off for no reason.
The switch was bad in my 04 7500 Topkick,messed up the heater air conditioning.A few other electrical gremlins disappeared with the old switch.
A friend with a 94 gasser had a bad switch mess with his tranny.He was going to take it to the tranny shop when i told him to check his switch.New switch all good.

Dealer overhauled the trans in my '95 because it wouldn't shift out of second. New ignition switch finally fixed the problem...

While the ignition switch can and does fail, and may cause any of the symptoms, the totality of the symptoms don't suggest the switch. MUCH more likely a loose connection at the starter solenoid power lug.

Dmax you hit the nail on the head my friend.
The batt cable going to the solenoid was loose, secured it now good to go.
Thank you guys so much for all the help.
I really appreciate it and you all, this is the 2nd time this sight saved me some money.
Thank you

My blower is not working now.
Is there a fuse box somewhere?

It's hard to tell with the Workhorse chassis, and depends a lot on the upfitter. It has at least a couple fuse boxes. Which Workhorse series is it? Who is the upfitter (Winnebago, Grumman, etc.)? Is it an RV, step van, etc.? It should have one under the dash, and one in the engine compartment, perhaps on the firewall, and may have other(s) depending on the application. Also note that, the chassis model year may not be the same as the upfitter's model year. For example, a 2001 M/Y Winnebago may use a chassis that varies from 2000 to 2002, depending on the model and actual build date. Look for the plant build tag on the frame for the actual GM chassis model year. If it's an RV, give a shout out to Arveetek for more detailed info (he's also a moderator in the Towing/RV forum).

Ok I did find two fuse box under the dash.
So I'll start there. It's a P42 GM other than that I'll need to do some research.
Thanks

OK, a step van then, and not other appointments (specialized application, like an RV)? If so, and the fuses are good, it's probably the resistor pack, usually located in an air duct. Often when they fail, the blower will only work at certain speed settings. If it has factory firewall A/C, it's usually located in the duct ahead of the evaporator. Look for an electrical connector that plugs into the duct, or a pigtail connector that goes to the duct. The thing it plugs into will be the resistor pack, and should be easily removed with obvious screw(s). You can confirm that power is getting to it (power will vary to the pole according to switch position), and that it has continuity to the switch/dial and to the blower motor.